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C 509724The
'Delft' system for mine ral identification
1.
Opaque minerals
The 'Delft' System for Mineral Identification
1. Opaq ue Minerals
R.A. Kühnel
J.J
. Prins
H.l. Roorda
Department of Mineral Technology
Delft University of Technology
Delft
, The Netherlands
Delft University Press/
1980
Delft University Press
Mijnbouwplein 11,
2628 RT Delft
(015) - 783254
Copyright © 1980 by Delft University Press, Delft
No part of this book may be reproduced in any form, by print, photoprint, microfllm
or any other means without written permission from the publisher.
ISBN 906275021 4
..
To our students
v
-Acknowledgements
The authors express their gratitude to Dr. N. F. M. Henry, editor of the first issue of IMA/COM Quantitative Data File, for his kind permission to publish an example of a card and the list of minerals included in the File.
The authors also thank the JCPDS - International Center for Diffraction Data, 1601 Park Lane, Swarthmore, Pa. USA, for the kind permission to publish three main lines of the common ore minerals and the numbers of X-ray diffraction cards of some other minerais, included in the 'Delft' System.
·Contents
PrefaceIntroduction Instructions for use The polished section The microscope Criteria References
List of symbols and abbreviations
Optica! categories Punched card code Reflectance classes
VHN classes Colour classes Textural criteria Chemica! criteria Free choice criteria Lists of minerals Postscript to users Index 001 - 006 101 - 108 201 - 208 301 - 306 401 - 408 501 - 533 Page 1 3 5 7 9 11 12 13 29 49 69 83 101 169 181 199 201 VII
Preface
The study of opaque minerals by means of reflected-light microscopy was introduced at Delft University of Technology by the late Professor A.H. van der Veen, about half a century ago, and ever since it has been part of the curriculum for students in mining and mineral engineering. Teaching students to identify minerals by means of reflected-light microscopy has always been a matter of considerable difficulty. However, the introduction of quantitative methods during the past decade has greatly facilitated this task and systematic tables listing reflectance values and micro-hardness data are available. Unfortunately, it has been our experience that beginning students have considerable difficulty in using these tables for a number of reasons. These inc1ude the inherent inaccuracies in determining the reflectance and micro-hardness values and the fact that these values show appreciabie overlap for different minerals.
The present system is based upon mineral identification by means of a number of semi-quantitative measurements and observations that can be obtained readily. The system has been used in the instruction of students for a number of years and has proven to be operabie. Following a course consisting of fifteen instruction periods, each of three hours duration, most students were able to identify any of the 195 'common' minerals listed in these tables. We wish to emphasize however, that our system is not intended to replace the available tables such as Uytenbogaardt and Burke's or those to be published by the COM. On the contrary, it has been our intention to facilitate the use of those tables.
Reflected-light microscopy obviously involves more than the use of determinative tables. Tables alone cannot teach the student to observe intelligently, or to operate his instruments properly. Nor do they provide an understanding of the physical significance of the measurements that are being made. This type of information must be supplied partly by the instructor and partly by reference to textbooks such as Galopin and Henry. The notes contained in the present text are not intended to be more than some comments of a general nature.
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The authors are mineral technologists, not mineralogists. They are therefore greatly indebted to Dr. M.l. Oppenheim of the Geological Survey of Ireland, who kindly undertook to write a thorough revision of our original draft and who greatly contributed to the elimination of errors in definitions, terminology and grammar. Our thanks are extended also to Professor W. Uytenbogaardt of the Free University of Amsterdam (recently at Delft University of Technology) for many stimulating discussions and for providing us with data on new minerals. Mr. E.A. Boer and Mr. C.H.F. Cordova Gaytan graduate students, have been of major assistance in organizing mineral data, in them entering in the system and in checking the system for errors. Also Mr. J.J.S. Steensma, research officer, gave valuable assistance in preparing the lists of minerals and reading the manuscript. We are grateful to Miss. M. de Groot for her assistance in getting the manuscript prepared for the publisher and to Mr. J. Swanink who prepared the illustrations. Finally, we would like to commend the Delft University Press for their preparedness to produce the tables in this rather unorthodox form.
Delft, 30 october 1979 R.A. Kühnel
J.J. Prins H.J. Roorda
Preface
The study of opaque minerals by means of reflected-light microscopy was introduced at Delft University of Technology by the late Professor A.H. van der Veen, about half a century ago, and ever since it has been part of the curriculum for students in mining and mineral engineering. Teaching students to identify minerals by means of reflected-light microscopy has always been a matter of considerable difficulty. However, the introduction of quantitative methods during the past decade has greatly facilitated this task and systematic tables listing reflectance values and micro-hardness data are available. Unfortunately, it has been our experience that beginning students have considerable difficulty in using these tables for a number of reasons. These include the inherent inaccuracies in determining the reflectance and micro-hardness values and the fact that these values show appreciabie overlap for different minerals.
The present system is based upon mineral identification by means of a number of semi-quantitative measurements and observations that can be obtained readily. The system has been used in the instruction of students for a number of years and has proven to be operabie. Following a course consisting of fifteen instruction periods, each of three hours duration, most students were able to identify any of the 195 'common' minerals listed in these tables. We wish to emphasize however, that our system is not intended to replace the available tables such as Uytenbogaardt and Burke's or those to be published by the COM. On the contrary, it has been our intention to facilitate the use of those tables.
Reflected-light microscopy obviously involves more than the use of determinative tables. Tables alone cannot teach the student to ob serve intelligently, or to operate his instruments properly. Nor do they provide an understanding of the physical significance of the measurements that are being made. This type of information must be supplied partly by the instructor and partly by reference to tex tbooks such as Galopin and Henry. The notes contained in the present text are not intended to be more than some comments of a general nature.
?
•
The authors are mineral technologists, not mineralogists. They are therefore greatly indebted to Dr. M.J. Oppenheim of the Geological Survey of Ireland, who kindly undertook to write a thorough revision of our original draft and who greatly contributed to the elimination of errors in definitions, terminology and grammar. Our thanks are extended also to Professor W. Uytenbogaardt of the Free University of Amsterdam (recently at Delft University of Technology) for many stimulating discussions and for providing us with data on new minerais. Mr. E.A. Boer and Mr. CH.F. Cordova Gaytan graduate students, have been of major assistance in organizing mineral data, in them entering in the system and in checking the system for errors. Also Mr. J.J.S. Steensma, research officer, gave valuable assistance in preparing the lists of minerals and reading the manuscript. We are grateful to Miss. M. de Groot for her assistance in getting the manuscript prepared for the publisher and to Mr. J. Swanink who prepared the illustrations. Finally, we would like to commend the Delft University Press for their preparedness to pro duce the tables in this rather unorthodox form.
Delft, 30 october 1979 R.A. Kühnel
J.J. Prins H.1. Roorda
Introduction
· .. data are less important than their interrelations.
R.A.K.
The use of punched cards for the identification of minerals is not new. The 'punched<ard' system, originating with Hollerith, has for long been applied in many branches of science and every-day life. The present tables possess a certain novelty in their SWING-OUT form, and they also permit the cards to be retained as a booklet.
It should be stressed from the outset that the purpose of the System is the identification rather than the description of minerals. Some of the observational criteria adopted are known to be unsuitable for say a scientific publication, yet quite adequate for identification. Thus we have not presented pleochroism as a phenomenon distinct from bireflectance, neither have we considered a mineral's colour in quantitative terms.
The System is amenable to expansion. There is no objective basis for deciding which minerals are common or which rare and we have arbitrarily se!ected 195 'common ore minerals'. Some transparent minerals are inc1uded (e.g. rutile and zircon) because of their frequent occurrence in ores and concentrates. Twenty positions are left vacant, and the user may add up to twenty minerals of his choice to the System, perhaps those with which he is personally concerned. Such additions would involve a suitable entry in the minerallist (page 184-5), and a punching of the margins of the appropriate Property Cards with the aid of a sharp steel tube of diameter 5.5 mmo
The System may also be extended with regard to the properties used for identification. Several blank cards are provided for this purpose. Such properties are unlikely to be of value unless they cover 10-25% of the mineral species; they must furthermore be amenable to a rigid definition. There are many useful properties which are not incorporated in these tables, particularly genetic features such as the presence of 'exsolution textures', 'orientated intergrowths', 'replacements', etc. A latter edition may wen include these, but there is not always uniformity in their use and interpretation. Before expanding the System it may be borne in mind that if a determinative scheme is to be economical it should be short; in other words, faster results are obtained with a smaller number of criteria.
All forms of chemical analysis - wet, microchemica!, spectral, electron-probe microanalytical, even etching - are both laborious and expensive. It is recommended that chemistry be called upon only where the faster methods do not give a definite result. Commonly any of a small number of minerals are matched by the properties observed, and in this case ajudicious chemica! test may wen decide between the candidates. Chemica! criteria in the tables refer only to elements having a concentration greater than 1%; minor elements are mentioned in the minerallists, ho wever.
Instructions for use
The System is very simple to use but the followingonotes may be of help. The System comprises three parts: Introductory Pages, Lists, and Property Cards. The use of the fust two parts is self-evident, and we deal hereunder with the Property Cards with which the process of identification is largely concerned.
The Property Cards: their use.
Each property considered to be diagnostically useful is represented by a separate 'Property Card'. Every Property Card has 216 numbered positions marked on its right-hand margin. Numbers 1 - 215 correspond each to a single mineral species; position number 216 is prepunchedand is reserved for Card alignment. As explained in the Introduction, the user may utilise positions 196 - 215 for additional minerals of his own choice.
The System will permit the identification of the 195 'common' minerals listed on pages 181-4; each mineral has its own serial number. This number has been punched by the printer on the appropriate Property Cards. Galena, for example, has the serial number 64. The mineral galena is optically isotropic, has a reflectance (measured at 546 mm) of 43-440/0, and a Vickers Hardness Number of
70-85. Position 64 will accordingly be found punched through on Property Cards number 001
('mineral is isotropic'), 104 ('mineral shows reflectance of 40-50%'), and 201 ('mineral shows VHN less than 100').
The booklet is bound by two screws along the lefthand margin. The upper screw is left c1osed. The lower screw is removed whenever a determination is to be made.
Mineral determination
Suppose the properties just given for galena had been noted (optically isotropic; R = 43.5%; VHN = 77). The determination would proceed as follows:
1. The lower binding screw is removed
2. The appropriate Property Cards are SWUNG OUT to the right (Cards 001, 104, 201). 3. The pre-punched holes of position 216, occurring in every Property Card, are brought into
alignment.
4. Minerals which possess all the observed properties will be immediately evident; their serial numbers will be replaced by a continuous hole through the Property Cards.
• • 0 .
• • • 0
0 . 0 0
0 0 0 .
A
0 0 . 0
00 • •
. 0 . 0
0 • • 0
B
0000
0 0 . 0
0000
0000
AnB
5. In the eventuality that more than one mineral is indicated by the selected group of Property Cards it is necessary to utilise a further property, or properties, in order to narrow the choice. In the example we have been considering there will be three such continuous holes, narnely positions 35 (c1austhalite), 41 (copper), and 64 (galena). Copper would then be distinguished from the other two minerals on the basis of its colour; and from Uytenbogaardt & Burke page 220 it is seen that clausthalite has a significantly higher reflectance at 546 nm (49.5%) than that measured (43.5%). The unknown mineral would be galena.
It can happen that only hole 216 is found to be continuous; in such a case the following possibilities should be considered:
a) the mineral is not common, and its properties have not been inc1uded in the System. b) an error has occurred during measurement. Errors easily arise if reflectivity is measured on an
imperfectly levelled surface, or microhardness deterrnined on too smaIl or too shallow a grain. c) the mineral property faIls beyond the range of published values.
d) an inadvertent fault has entered the production of this work, notwithstanding the care expended to prevent such a happening. Should such a case be detected the investigator is earnestly requested to alert the authors in order that the error may be corrected in a later edition.
In the light of experience we would make the following recommendations for working with the System.
i) work systematicaIly; from the more important criteria (optical category, reflectivity, VHN) to the less important properties (colour, texture, internal reflection, etc.); chemical testing need be applied only for distinguishing between otherwise similar minerals.
ü) repeat measurements on several grains whilst paying attention to the grain orientation: many properties show anisotropy even in cubic crystals.
ili) record all the observed and measured data; sketches should be made to show the relationships between the mineral being measured and those surrounding it, and also the points within the mineral at which measurement was effected.
The Property Cards: their lay-out
Each card states fustly the PROPERTY to which it refers. All minerals which show this property are punched in the right-hand card margin. Where a mineral shows a range ofproperties, that mineral's position is punched on more than one card.
The following CRITERIA section attempts to define the property in terms of observations which can be made with the microscope.
The REMARKS section gives additional details which will aid in recognizing the property, and points out possible complications.
TYPICAL EXAMPLES ofvery common minerals showing the appropriate property are listed at the card base.
An additional feature to each card is the listing on its back of all the minerals reported in the literature to the end of 1978 which are not included in the System proper but which show the property covered by that card. These lists give the name, the principal optical properties, the microhardness, the principal elements present, and references to fuller descriptions in three major texts. By inspection of these lists the user may be alerted to the possible identity of a rarer mineral even though the System would not lead him to its direct determination.
,
The polished section
The microscopie determination of opaque minerals is carried out on polished sections. A polished section ideally is bounded by a single plane surface which is smooth and free of scratches. In practise it is impossible to achieve these conditions; where adjacent minerals have different hardnesses, polishing results in the formation of a micro-relief because harder minerals are wom Ie ss than weaker minerals.
The preparation of a polished section entails several stages: i. cutting a chip off the original specimen with a diamond saw Ü. mounting the sawn chip in plastic
ili. grinding the surface of the mounted specimen with abrasives ivo polishing the ground surface
Cutting produces an initial nearly-flat surface. A slice will need to be trimmed to a size smaller than that of the mount. Most polished sections are about 2 to 5 cm' in area, and round.
Mounting is now generally carried out in cold-setting plastic, for the following reasons: I) small samples are easy to handle when so embedded, 2) the plastic holds any loose grains and supports weak or fractured ores, 3) the plastic impregnates porous materials and facilitates their cutting along a required direction, 4) the plastic being poured into fixed moulds permits the preparation of sections having a standard size, which size can be chosen to suit an electron probe microanalyser sample holder.
Two main techniques are available for the mounting of ores in plastic
A. Mounting by embedding into solid plastic at an elevated temperature under pressure
B. Mounting by embedding in liquid plastic at room temperature and pressure (or at a temperature
and pressure only slightly elevated)
The high temperatures required by the solid plastics could affect the original composition of certain samples, and solid plastics are according seldom used by mineralogists. The liquid plastics are usually
made up from two components - a base and a hardener. Hardening takes place in a small mould in
a period which wi11 vary downwards from several hours in accordance with the therm al treatment and
specific brand used. Any of the many available brands is suitable if, when solid, it will be transparent and mechanically, thermally and chemically stabie. Before mounting, all traces of fat should be removed from the sample using alcohol or acetone; this is especially important if fine-grained powders or flotation produets are to adhere properly to the plastic.
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-:
iiiliiiililiii!lii1ilil!i::i., ..
:
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-Grinding removes the deeper scratehes and irregularities from the sawn surface. Grinding is done in stages using abrasives of decreasing particle size; in many cases it may suffice to use grades 600 and 1,000 only. The period of grinding at each stage will depend on the nature of the specimen: harder minerals require a longer grinding time. Fully automatic machines are available for grinding several specimens simultaneously. lt is advantageous to grind a bevel around the section circumference before commencing grinding proper. It is necessary to subject the specimens to a thorough cleaning in an ultrasonic bath between each grinding and polishing stage; in this way any loose particles which could damage the surface at a later stage are removed. It should be ensured that the ground surface is truly planar, for with use the machine's grinding surfaces may become wom and require periodic truing.
Polishing is the final and most difficult stage of the preparation. Polishing is to some extent an art. Different minerals will require differing polishing materiais, differing wetting fluids, different polishing times, and different applied pressures. In dealing with multi-phase ores the production of well-polished surfaces is possible only following long experience coupled with a certain sensitivity. The most commonly used polishing agents are alumina (either in suspension or as a paste) and diamond paste. Iron oxide and chromium oxide are less important. Wetting agents differ in their composition and viscosity, and include water, water plus detergent, kerosine, alcohol and various oils. Specialised techniques are available for polishing metals.
Polished thin-sections have recently become popular because a single preparation permits both
transmitted-and reflected-light examination. A polished thin-section, however, is too thin to permit microhardness measurements to be made for which purpose the standard plastic mount is required.
Some minerals are chemically unstable in the atmosphere, whilst others react with certain polishing or wetting agents. Thin superficial films of reaction produets can be formed which mask the true
colour of amineral. Argentite, for example, rapidly turns black by the action of atmospheric S02'
Bomite tarnishes fairly rapidly. Some minerals wi11 tamish in a matter of hours or days, e.g. pyrrhotite, chalcopyrite, umangite, berzelianite, and others. FOT this reason it is advisable to repolish a section lightly before observation and measurement.
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---The micro scope
The identification of opaque minerals is based on the microscopic, observation and measurement of a polished section in reflected light. A properly adjusted ore micro scope is therefore an important prerequisite. An ore microscope differs from other polarising micro scopes in its special illumination unit. Polarised light passes downwards through the objective lens to be reflected from the polished surface of the ore mineral.
Transparent minerals appear dark under the ore microscope because they reflect only a small part of the incident light. Opaque minerals, on the other hand, appear light because they reflect a greater part of the incident light. A process additional to that of transmission and reflection is the absorption of light by the mineral. A further process can take place in crystals having low symmetry, namely the rotation of the vibration plane of both the trans~itted and reflected polarised light.
A microscope is not properly adjusted unie ss due attentioh has been paid to the following points:
provision of a really strong light source, and an even illumination of the field. Quartz halogen lamps are particularly suitable, for their spectral output is sirnilar to that of daylight in addition to the fact that their output is high.
polarisation of the incident light should be perfect, and the orientation of the polariser's vibration plane should be known. The analyser should be amenable to precise 'crossing', although the facility for rotating it from the crossed position is convenient.
the illumination should be able to provide illumination truly perpendicular to the specimen surface.
all the objectives should be centered and clean. Low- and medium-power objectives should be available.
the field- and aperture diaphragms should be centered and adjusted to cut off stray light.
the stage, which should be rotatabie, must be level, that is to say, perpendicular to the optic axis of the microscope.
the polished sections under examination are preferably mounted on specialievelling holders: in the absence of such holders samples can be pressed flat on to plasticene supported by a glass slide.
The microscope and its surroundings should be kept clean.
For the measurement of reflectance and microhardness additional instruments become necessary.
The measurement of reflectance and bireflectance requires a device to pro duce monochromatic light, a photocell (preferably with a photomultiplier), and a galvanometer to indicate the light-level. Monochromatic light can be produced either by a monochromator, a graduated interference fIlter,
or a set of discrete interference fIlters.
The light source should incorporate voltage stabilisation for accurate work. As reflectance measurement is comparative, at least one reflectance standard is required. Three standards are recommended by the COM:
NG (neutral glass) with a reflectance of about 4% SiC (silicon carbide) with a reflectance of about 21 % WC (tungsten carbide) with a reflectance of about 46%;
the precise reflectance values of these standards are supplied by the manufacturer after individual calibration through the visual spectrum. Devices for printing out or recording the light intensities indicated by the galvanometer are convenient but by no means necessary. Indeed, for the purposes of identification of a mineral, as against its description, useful work can be do ne by measuring reflectance in white light, or, preferably, at the single wavelength of 546 nm.
The measurement ofindentation microhardness can be performed either on a specialised instrument, or on the ore microscope itself utilising attachments. A specialised rnicrohardness tester will embody a microscope for viewing the specimen to be tested. The essential parts, either for a separate instrument or for the attachment accessory, are a special diamond point, a variabie set of weights, a device for applying the weights behind the diamond point, and an eyepiece micrometer for viewing and measuring the resulting indentation.
The following Table shows the microscopie adjustments required for cartying out the measurements or observations partinent to the Determinative Tables of this booldet.
Criterion Colour
Structure & Texture Minera! interrelations Oeavage Pleochroism (Zoning) Anisotropy In terna! reflection Twinning Zoning Reflectance Bireflectance Microhardness
8
AccessoryAny convenient objective
Daylight filter
Low or medium power objeetive
Maximum illumination Monochromatic light No daylight or green mter Indenter
Green filter Micrometer eyepiece
Adjustment Parallel polars
Diaphragms set for optimum resolution
Crossed polars Diaphragms open
Diaphragms elosed
Diaphragms set for optimum resolution
Criteria
The System is based on the use of 'Property cards'. Of ten a large number of minerals may show the same general property, and for purposes of identification it is desirabie to subdivide that property into arbitrary defined classes. When such a subdivision is made it is obviously critica1 that the border of the classification be clearly defined. We are using the term criteria as a defmition of the means by which a particular property may be recognised or measured.
This edition, for example, utilises reflectances subdivided on the basis of the following criteria: R
<
20%, 20-30%, 30-40%,40-50%,50-60%, and>
60%. Bireflectance is classified according to the criteria (R2 -Rl)<
2%, 2-4%,4-8%, and>
8%. Similarly microhardness limits of 100, 200, 300,400,600, 800, and 1000 VHN divide minerals into 8 classes based on easily recognised criteria. Ideally, perhaps, an identification system would have its criteria so selected that the number of minerals in each class were approximately equal; but with the discovery of new minerals such anallocation would break down. The number of minerals in the present System's classes is far from
uniform.
The choice of criteria
Both quantitative and qualitative criteria can be used for mineral identification. A selected criterion can be of value only if it can readily be recognised or measured with relative precision, and if it is a regular feature of the mineral. We accordingly distinguish three grades of criteria, recognition of which should aid the reader to adopt discrimination in his use of the System.
l. PREFERRED criteria 2. SECONDARY criteria i. optical categories isotropism anisotropism (unclassified) reflectance (by classes)
bireflectance (only if R measurement is ± 0.5%)
ü. chemical composition
VHN (vulnerable to numerous errors)
degree of anisotropy (dependent on grain orientation and intensity of illumination)
colour (subjective)
internal reflections (not constant)
3. MARGINAL criteria
texture and structure (not constant) shape (recognition requires experience)
The criteria of lesser value have been included in the System even though they can be considered diagnostic for only a limited number of opaque minerals. But the availability of these criteria may encourage the reader to adopt a broader outlook in his determinative work; and textural features have an importance of their own in the realm of geology as weil as mineral technology.
Overlapping
As a consequence of anisotropy, structural imperfection and diadochy many minerals show properties
which extend over a range of values. This holds both for chemical composition and for physical
properties. Accordingly a particular 'property' of a given mineral may properly be expressed in more
than one class; we refer to this spread as 'overlapping'. But even were the properties of minerals have exact values there would still be an apparent overlap caused by uncertainity in, and errors of, measurement. Pyrolusite, for example, occurs with an extremely broad range of VHN; the occurrence
of trace elements can affect a mineral's colour. As aresult, the same mineral may properly be described
by several criteria, and so belong to several classes. Unfortunately even our preferred optical criteria cannot always be applied unequivocally because they are based on published measurements which
have not always paid due attention to the orientation of the sections described. We recommend that
only single crystals - in distinction to crystal aggregates - be studied, with careful attention given to their orientation. Where it is unavoidable to base an identification on unfavourable crystals then this fact should be mentioned in any publication.
An additional reason for the existance of overlapping is the arbitrary nature of the boundaries given to the criteria of a class; for it may weil occur that the values of a measurement overlap a class boundary.
Free choice criteria
The System is 'open'. There is freedom for both extending it, or refining it, according to the
requirements of local problems or in response to personal predilections. Five blank sheets are provided
for this purpose. Some users may care to subdivide perhaps the most populated reflectance class 30-40o/q whereas others might consider the recognition of new textural criteria to be of significance; and so on. The authors would appreciate being informed of any modification to the System effected by its users.
liST OF APPliED CRITERIA:
Code Keyword Symbol Group
001 Mineral is isotropic I
002 Mineral is weakly anisotropic WA
003 Mineral is distinctly anisotropic DA OPTICAL
004 Mineral is strongly anisotropic SA CATEGORIES
005 Mineral is extremely anisotropic EA
006 Mineral shows internal reflections IR, ir
101 Mineral has reflectance <20% < 20
102 Mineral has reflectance 20 - 30% 20 - 30 501 Mineral contains silver Ag
103 Mineral has reflectance 30 - 40% 30 - 40 502 Mineral contains aluminium AI
104 Mineral has reflectance 40 - 50% 40 - 50 REFLECTANCE 503 Mineral contains arsenic As
105 Mineral has reflectance 50 - 60% 50 - 60 CLASSES 504 Mineral contains gold Au
106 Mineral has reflectance >60% > 60 505 Mineral contains bismuth Bi
107 Mineral has bireflectance < 4% <4 506 Mineral contains calcium Ca
108 Mineral has bireflectance 4- 8% 4-8 507 Mineral contains cobalt Co
109 Mineral has bireflectance > 8% >8 508 Mineral contains copper Cu
509 Mineral contains germanium Ge
201 Mineral shows VHN < 100 < 100 510 Mineral contains iron Fe
202 Mineral shows VHN 100 - 200 100 - 200 511 Mineral contains mercury Hg
203 Mineral shows VHN 200 - 300 200 - 300 512 Mineral contains water as H,O or (OH) H,O
204 Mineral shows VHN 300 - 400 300 - 400 VHN 513 Mineral contains magnesium Mg
205 Mineral shows VHN 400 - 600 400 - 600 CLASSES 514 Mineral contains manganese Mn
206 Mineral shows VHN 600 - 800 600 - 800 515 Mineral contains molybdenum Mo
207 Mineral shows VHN 800 - 1000 800 - 1000 516 Mineral contains niobium and tantalum Nb+Ta
208 Mineral shows VHN > 1000 > 1000 517 Mineral contains nickel Ni
518 Mineral contains oxygen 0 301 Mineral is distinctly coloured: yellow-cream-orange y 519 Mineral contains lead Pb
302 Mineral is distinctly coloured: pink-red-purple-violet r 520 Mineral contains platinum metals Pt-m CHEMICAL
303 Mineral is distinctly coloured: blue-green bg COLOUR 521 Mineral contains sulphur S CRITERIA
304 Mineral is distinctly coloured: beige-bronze-brown br CLASSES 522 Mineral contains antimony Sb
305 Mineral is not distinctly coloured: white-grey w 523 Mineral contains selenium Se
306 Mineral tarnishes ta 524 Mineral contains silicon Si
525 Mineral contains tin Sn
401 Mineral occurs in isometric crystals a 526 Mineral contains tellurium Te
402 Mineral occurs in elongated crystals ab 527 Mineral contains titanium Ti
403 Mineral occurs in bladed crystals abc 528 Mineral contains uranium U
404 Mineral occurs in dendritic crystals d TEXTURAL 529 Mineral contains vanadium V
405 Mineral shows zoning z CRITERIA 530 Mineral contains tungsten W
406 Mineral shows twinning t 531 Mineral contains zinc Zn
407 Mineral shows c1eavage x 532 Mineral contains zirconium Zr
408 Mineral shows colloform textures 0 533 Mineral contains other elements OE
References
BERRY L.G. et al. (editors)BOLEWSKI A.
BOWIE S.H. U., TAYLOR K. BOWIE S.H. U.,
FONT ALTABA M.
BOWIE S.H.U., SIMPSON P.R., ATKIN D. CASEY R.S., PERRY J.W., BERRY M.M. FEIGEL F. FREUNDH. GALOPIN R., HENRY N.F.M. HENRY N.F.M. (ed.) HÖFERT H.J. ISAKOWP.M. McLEOD C.R., CHAMBERLAIN J.A. PICOT P., JOHAN Z. PILLERH. (1974) (1951) (1958) (1970) (1975) (1958) (1954) (1966) (1972) (1977) (1957) (1955) (1968) (1977) (1966)
- Selected Powder Diffraction Data for Minerals (Search Manual) Joint Comrnittee on Powder Diffraction Standards. Swarthmore, Pennsylvania U.S.A. - Determination of Minerals (in Polish) - Inst. of
Geology Warsaw
- A system of ore mineral identification, Mining Magazine, 99:265-77, 337-345
- International Tables for the microscopic determination of crystalline substances absorbing in visible light-Barcelona
- Reflectance measurements in monochromatic light on the Bowie-Taylor suite of 103 ore minerals Forschr. Miner, 52:567-82 Spec. Issue
- Punched cards. Their applications to science and industry - Chapman & Hall Ltd. London
- Spot tests Vol. I - Elsevier Publishing Co. Amsterdam - Applied Ore Microscopy - The Macmillan Co. New
Vork
- Microscopic Study of Opaque Minerals - W. Heffer and Sons Ltd. Cambridge
- IMA/COM Quantitative Data File First Issue June, 1977
The Applied Mineralogy Group of the Mineralogical Society, London.
- XYZ in the realm of colours. Zeiss Werkzeitschrift 24.
- Analyse chimique qualitative des minerais et rninéraux par la méthode de broyage des poudres. Edition d'etat scientifique-technique. Moscow Reflectivity and Vickers Microhardness of Ore Minerals. Geol. Surv. of Canada Paper 68 Atlas des Minéraux Métalliques, Mémoires du B.R.G.M. No 90
Colour measurement in ore microscopy. Min. Deposita 1: 175-92
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----PILLER H. PRINS J.J. RAMDOHRP. ROSICKY V., KOKTA J. ROST R. ROST R. SCHOUTENC. SHORT M.N., UYTENBOGAARDT W., BURKE E.A.J. VEEN v.d. A.H. VOLYNSKIJI.c.
YOUNG B.B., MILLMAN A.P.
(1974) (1973) (1960) (1969) (1961) (1961) (1962) (1962) (1940) (1971) (1925) (1947) (1964)
A
z
Modern Techniques in reflectance measurements. Journ. of Microscopy 100:35-48
Instructions for Microscopic Determination of Minerals in Reflected Light. University of Technology Delft
- Die Erzmineralien und ihre Verwachsungen. Berlin The ore minerals and their intergrowth. Pergamon Press Oxford
- Handbook for Mineral Identification (in Czech) -Czech Acad. of Sciences Praque
Microchemical determination of minerals (in Czech) -State Pedag. Publ. Prague
- Heavy Minerals (in Czech) - Czech Acad. of Sciences Prague
- Determination Tables for Ore Microscopy - Elsevier Publishing Co. Amsterdam
Microscopic determination of the ore minerals. Bull. U.S. Geol. Survey. No. 914
Tables for Microscopic Identification of Ore Minerals - Elsevier Publishing Co. Amsterdam
Mineragraphy and ore-deposition, Vol. I The Hague Determination of Ore Minerals under Microscope (in Russian) - State Publ. Geol. Books, Moscow - Microhardness and deformation characteristics of ore
minerals, Trans. Inst. Mining Metal. 73:437-66
LIST OF SYMBOLS AND ABBREVIATIONS' I WA DA SA EA ?A IR ir ? n.d.
+
*
RRe
Rl-R2 Rg-Rp Pt-m U+B RA &h COM ASTM ASTM dhkl 7.10x 5.116 a ab abc d12
isotropic weakly anisotropic distinctly anisotropic strongly anisotropic extremelyanistropic anisotropic (not specified)abundant internal reflections rare internal reflections unknown distinct property not present no data present in approximately
element in minor quantity overlap with neighbouring classes reflectance in
%
generallyreflectance in
%
in defined direct ion e bireflectance in%
on a random section bireflectance in%
on specified optical plane platinum metalsreference to the page of W. Uytenbogaardt and E.A.J. Burke (1972) reference to the page of P. Ramdohr (1969)
reference to the tab Ie ofC. Schouten (1962) Commission on Ore Microscopy
American Society for Testing and Materials
file no.2 XRD card (from 1969 selected Powder Diffraction Data of Joint Committee on
Powder Diffraction StandardS} distance of structural planes hld dhkl value of the main line (in A)
dhkl value of one of main lines and its relative intensity isometric crystal
elongated crystal bladed crystal dendritic crystal
o colloform tex ture
t twinning
z zoning
x cleavage
ta tarnishing OE other elements
Note: ' Further symbols and abbreviations see Report of the Committee on Symbols & Defrnitions published in Mineralogy & Materials News Bulletin for Microscopic Methods Edited by N.F.M. Henry (1975).
2 Because of systematic growth and refining of X-ray data me, the user is advised to search in
Optical categoties
The behaviour of opaque mineraIs in reflected light is somewhat complicated. We restrict ourselves to mentioning a few aspects of the subject which concern the optical criteria utilized by this determinative system.
Anisotropy
The physical properties of crystals are, in general vectorial: a measured property is unique only for a specified direction within the crystal. This statement holds for all physical properties. The degree of variance which a crystal may show in the values (scalar) of a particular property measurable along different directions within that crystal is called the ANISOTROPY of the crystal for that property. The anisotropy of a crystal is controlled by its structure, that is to say by its symmetry, its lattice dimensions, and its bonding forces. The degree of anisotropy, as well as its spatial disposition, may differ for different properties of the crystal. Where a crystal shows, for a certain property, the same values for all directions of measurement then the anisotropy is zero and the crystal is said to be ISOTROPIe for that property. Highly symmetrical cubic crystals exhibit constant optical properties in all directions, and hence they are optically isotropic; with respect to their microhardness, however, such crystals may yet be anisotropic. Amorphous mineraIs phases, e.g. psilomelane, behave as if they were isotropic.
Some mineraIs show considerable anisotropy of the microhardness, graphite for example. But in view of the generallack of precision currently associated with microhardness measurement the degree of rnicrohardness anisotropy is not utilized as a practical diagnostic criterion.
An assessment of the rnineral's optical anisotropy is an important feature of the 'Delft' System. The degree of optical anisotropy may be detected in two ways, the one qualitative, the other quantitative. On inspection of the mineral in white light and under crossed polars (or nearly crossed polars) anisotropy if present will be revealed by the presence of interference colours which altemate with four ex tinction positions as the micro scope stage is rotated through 3600
• The degree of anisotropy can be estimated visually from the intensity of these interference colours.
Quantitative 'bireflectance classes' can be established by measuring the range of reflectance values exhibited by suitable oriented grains of the mineral during the rotation of the microscope stage through 3600
• Unlike anisotropy, which is detected in white light, bireflectance can be measured in either white or better monochromatic light.
It must be emphasised that inspection of any optical property of an anisotropic crystal must take into account the orientation of the crystal grain. Different grains of the same mineral can yield quite different values for each optical property (reflectanee, bireflectance etc.), even colour. As
z
z
it is of the essence of succesful microscope technique that the factor of orientation be taken properly into account we discuss the matter a little filIther in the following sections.
The orientation of an iso tropie erystals
Reflectance is not a fundamental property of crystals: rather is it determined by the interplay of the crystal's refractive index, absorption coefficient and optical activity. For both the refractive index and absorption coefficient the crystal's anisotropy can be represented by a 'direction surface' (which in the case of refractive index is called indicatrix), but the two 'direction surfaces' are in general distinct. The resulting reflectance values are not portrayable by a simple ellipsoid but by a complicated high order direction surface defined by a tensor of higher orders. This fact is often overlooked.
As it is found that certain sections of an anisotropic opaque crystal will show a minimal or zero bireflectance reading, such sections are regarded as being cut perpendicularly to what we call an AXIS OF ISOTROPY - a direction crudely analogous to the 'optie axis' of transparent crystals. MineraIs of tetragonal and hexagonal symmetry have one such axis of isotropy and are called UNIAXIAL. Orthorhombie, monoclinic and triclinic crystals, possessing two such directions, are termed BIAXIAL.
A determination of the uniaxiality and biaxiality of an opaque mineral is not an elementary procedure, and the uniaxial or biaxial categorisation is not included in the present edition. The reason for this is that no routine procedure is currently available for recognizing directly the optical orientation of a given opaque mineral section - in distinction to the situation obtaining for transparent mineraIs.
Differently oriented sections of amineral will yield different values for a particular property, eg. reflectance, and measurement of several grains will yield values which fall within a range. However, of this range it is only the highest and lowest values of each property which are characteristic of the rnineral. In the absence of direct criteria for determining an opaque mineral's orientation it is necessary to examine sufficient a number of sections to ensure that these extreme values have been encountered. In practice, sections to be subjected to quantitative measurement may be limited to those which under crossed polars, in white light, show relatively strong interference colours. Anisotropy classes
As explained în the paragraph 'Anisotropy', the degree of a mineral's optical anisotropy may quantitatively be estimated from the intensity of the interference colours seen under crossed polars. As the stage is rotated, under crossed polars, four extinction positions will be encoutered, not necessarily at 900
to each other.
It is essential when searching for anisotropy to use very strong white illumination. The presence of anisotropy may be seen more clearly ü the micro scope polars be slightly uncrossed (up to 5°). Four arbitrary classes of optical anisotropy may be recognized, their particular features being explained on the appropriate 'Property Cards'. However, the intensity of the observed interference colour for a given degree of anisotropy is very much a function of the mineral's reflectance. Minerals having a low reflectance show relatively weaker colours in the same class of anisotropy than minerals having a stronger reflectance.
Scratches across the mineral surface also give the false effect of anisotropy and the resulting colours must be carefully ignored.
25 49 73 97 121 145 193
PROPERTY
Mineral is ISOTROPIC (001)98 146 170 194
CRITERIA Under crossed polars, when the stage is rotated, the field remains dark without any change in either colour or intensity.
99 123 147 195
REMARKS The degree of darkness shown by an isotropic mineral under crossed nicols will depend on the intensity of the light source
and perfection of the crossing of the polars. If the polars are accurately crossed then isotropic minerals will appear black. 100 124 148 172 _ 196
- Anisotropic minerals cut perpendicularly to their axis of isotropy will have a similar appearance; it is necessary to exarnine
5 29 125 149 173 197
several sections of a mineral in order to establish whether it is anisotropic.
- Scratches on the surface of a polished section can give a false impression of anisotropy: this effect is more noticeable at 6 30 126 150 198
high magnification.
- Intemal reflections can disturb the determination of isotropy. 31 79 103 127 151 199
TYPICAL 8 32 56 80 104 128 152 200
EXAMPLES: GALENA, PENTLANDITE, SPHALERITE
9 57 81 105 129 153 177 201
10 34 58 202
OTHER ISOTROPIC MINERALS
203
Mineral Optical Reflectance VHN Intemal References Composition
e
category
%
range reflection U+B Sch RA 12 60 204DZHALINDITE '\18.2 n.d. 136 In OH SUKULAITE 13-15? <800 IR 208 Ta Nb Sn 0 205 MANGANOSITE 13.7-14.9 314-325 IR 338 20d 883 MnO DZHEZKAZGANITE 15-30 '\,,230 86 Cu Re S 206 MAGNESIOFERRITE 16-18.0 627-925 170 Mg Fe Mn Al Ti 0 MURDOCHITE 16.3-17.6 519-657 166 Cu PbO 207 ULVOSPINEL <20? n.d. 170 7b 902 FeTiO WUESTITE <20? n.d. 166 883 FeO ONOFRITE -+ 20-28? n.d. 76 Hg S Se 88 112 136 160 184 208' ARGYRODITEr -+ 21.5-24.4 133-172 256 8e 12a 14 476 Ag Ge Sn S CANFIELDITE COULSONITE '\125 n.d. 172 7b 895 FeVO 65 89 113 137 161 209 COLUSITE 25.9-31.6 296-376 108 3a 556 Cu As Sn V Fe Sb S INDITE 26.8-29.3 293-325 136 692 Fe In S 66 162 210 STILLEITE -+ '\130 n.d. ir 216 517 Zn Se SCHWAZITE '\130 262-373 106 Ua 555 Cu Sb Hg S 19 43 67 163 211 TIEMANNITE -+ '\,,30 26-39 216 Ub 16b 519 HgSe GOLDFIELDITE 31.5-32.0 n.d. 106 562 Cu Te Sb S AGUILARITE -+ 32.0-35.5 25-35 218 Ub 12a 16b 475 Ag Se S 20 44 164 188 212 COLORADOITE 33.9-36.6 23-35 234 Ub 15b 520 HgTe SCHIRMERITE -+ '\,,35 n.d. 282 21b 736 Pb Ag Bi S 21 45 93 117 141 165 189 213 PENROSEITE '\,,35 407-550 218 16b 806 Ni Co Cu Se TRÜSTEDTITE 35-40? n.d. 220 691 Ni Se 22 70 94 118 142 166 190 214 TYRRELLITE 35-40 336-469 220 691 Co Ni Cu Se
LAURITE 37.2-48.0 1393-2167 322 19a 808 Ru S Os·lr·
HOLLINGWORTHITE 40-45 657-848 322 Rh Pt Pd Ru Ir As S 47 71 95 119 143 191 215
IRARSITE 45.2-47.8 '\,,976 322 lr Ru Rh Pt As S
MALDONITE 50-60 n.d. 72 340 Au Bi 24 48 96 120 144 168 192
SPERRYLITE 52.0-55.5 960-1277 324 19a 809 Pt As
THE 'DEUT SYSTEM FOR MINERAL IDENTIFICATION: I: OPAQUE MINERALS - COPYRIGHT © 1980 DELIT UNIVERSITY PRESS
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Mineral Optica! Reflectance VHN Intema! References
category
%
range reflection U+B Sch.MICHENERITE '\/56 n.d. 324
ANTIMONIAL SIL VER >60 n.d. 80
POTARITE '\/60 n.d. 324 6c 19a LEAD 60-65 4-6 36 AUROSTmITE '\/61 248-262 72 ZVYAGINTSEVITE 61.4-66.7 241-318 326 WHITNEYITE 'V63 '\/58 114 6b GEVER SITE 'V65 n.d. 326 PALLADIUM '\/70 n.d. 326 19a OSMIRlDIUM 75.8-80.0 297-645 328 19b IRIDIUM 78.2-80.8 n.d. 328
ADDITIONAL MINERALS (References see via 'index' in supplementary lists of minerals or on XRD cards)
TANT AL-AESCHYNITE GALKHAlTE
UNNAMED Ag, Sb, Te S min. FISCHESSERITE HAKITE CARLSBERGITE KRUfAlTE ISOMERTIEITE BOROVSKITE UNNAMED Pd, Pt, Sn, Pb min. INSIZWAITE UNNAMED Pt, Pd, Sn min. STISTAITE BlDEAUXITE BRUNOGEIERITE HAXONITE KITTLITE 14.0-14.5 19.9-26.1 27.7-39.0 32.2-33.8 32.8-33.6 40.5-49.5 41.5-44.6 45.23-58.80 53.3-61.2 57.0-63.6 61.1-61.7 61.2-65.9 78.0-82.5 n.d. n.d. n.d. n.d. 657-673 171-205 n.d. 31.9 352 >1000? 243-258 587-597 88.3 360-382 488-540 436-454 103-127 n.d. n.d. n.d. n.d. IR IR n.d. n.d. n.d. n.d. n.d. RA 813 364 341 811 393 342 355 344 Composition Pd Pt Bi Te Ag Sb PdHg Pb Ag* Sb* Au Sb Pd Pt Pb Sn Cu As Pt Sb Pd !rOs Ir Ca Y Ce Th U Ta Ti NbFeO HgAsS Ag Te S Sn Ag Cu Au Se Cu Sg Sb As Se S CrN Cu Co Ni Se Pd Cu As
Sb
Pd Sb Te Pd Pt Sn Pb Pt Bi Pt Pd Sn Sn Sb Pb Ag Cl F OH GeFeO FeNiC HgAgCuSSe73 97 121 145 169
PROPERTY Mineral
isWEAKL Y ANISOTROPIC
(002)e
26 50 98 122 146 170 194CRITERIA Under crossed polars, or nearly crossed polars, the mineral shows a slight but noticeable brightening (generally in shades of
123 171
grey) and four extinction positions within one revolution of the stage. 3 27 75 99 147
REMARKS 76 100 124 148 172 196
- The intensity of the brightening depends very much on the light source. Use of the strongest illumination available is 77 101 149 173 197
recommended with all diaphragms open.
78 102 126 150 174 198
- The anisotropic brightening is a function of the section orientation. For detennination of the degree of anisotropy it is the maximum brightening which is considered.
79 103 127 151 175 199
- Remember that weak anisotropy of high and low reflectance minerals produces a quite different effect; the colours, under crossed polars, can be quite vivid if the reflectance is very high.
8 32 56 80 104 128 152 200
- Anomalous anisotropy can be caused by internal tension and by extern al stress. Mechanically stressed isotropic mineraIs
105 129 153 177 201
can show weak anisotropy in some ores. A similar effect may be produced by too rigorous apolishing. 9 57 81
TYPICAL 10 34 58 82 106 154 178 202
EXAMPLES: CHALCOPYRITE, BORNITE, WOLFRAMITE
11 35 83 107 131 155 179 203
Anomalous: PYRITE, TIT ANOMAGNETITE
ee
12 84 132 204
OTHER WEAKL Y ANISOTROPIC MINERALS
e
37--
85-
133 157 181 205Mineral Reflectance VHN Internal References Composition 86 110 134 158 206
%
range reflection U+B Sch RA•
IXIOLITE 13-14 860-947 IR 200 Ta Fe Sn Nb Mn 0 15 39 63 87 111 135 159 183 207 CALZIRTITE 'V15 626-1035 IR 188 Ca Zr Ti Fe 0 FREUDENBERGITE 15-20 n.d. IR 182 Na K Ti Nb Fe Si 0 OH 16 64 88 136 160 184 208' PLUMBOFERRITE 15-20 n.d. 184 943 PbFeO FORMANITE <20 772-870 IR 202 YTaOBISMUTOTANTALITE 'V20 764-824 IR 200 Bi SbTa NbO 17 41 65 89 113 137 161 209
CADMOSELITE 'V20 203-222 ir 216 573 Cd Se
MINIUM 'V20 <100 IR 50 PbO 42 66 90 114 138 162 186 210
SAKURAIITE 'V20 n.d. 308 562 Cu Ag In Sn Zn Fe S
STIBIOT ANT ALITE
...
'V20 441-607 IR 200 Sb Ta NbO19 43 163 187 211 MASSICOTITE 'V20 <100 IR 50 PbO MAGNETOPLUMBITE
...
20.7-24.9 841-868 ir 184 943 Pb Fe Mn Al Ti 0 ROQUESITE 21.4-24.2 'V241 98 537 Cu In S 44 68 92 116 140 164 212 KESTERITE 22.7-27.1 320-322 310 553 CuSnZnS GETCHELLITE 24.3-30.7 30-50 IR 42 As Sb S 45 93 117 165 189 213 BERNDTITE 'V25 n.d. IR 308 Sn S BRIARTITE 26.0-27.6 100-300? 90 566 Cu Fe Zn Ge S 46 70 94 118 142 166 214 SAMSONITE 'V28 n.d. IR 260 914 778 Ag Mn Sb SWElS SITE 'V30 n.d. 234 15a 417 Cu Te
BILLINGSLEYITE 'V30 n.d. ? 260 Ag As Sb S 23 47 71 95 143 167 215
CUPROBISMUTITE
...
30-50? n.d. ? 294 707 CuBiSLENGENBACillTE
...
34.0-37.0 29-40 300 22b 744 Pb Ag Cu As S24 72 96 120 144 168 192
GIESSENITE 'V35 '\165 290 Pb Cu Bi SbS
Mineral Reflectance VHN Internal References Composition
%
range reflection U+B Sch RACROOKESITE 'V35 101-141 218 16b 477 Cu Tl Ag Se WITIICHENITE 35-40 161-216 292 21b 709 Cu Bi S DIAPHORITE 37.5-43.8 197-242 264 14 735 Pb Ag Sb S NUFFIELDITE 38.6-45.6 149-178 292 Pb Cu Bi S CHAOTITE 'V40 n.d. 104 C ARSENOLAMPRITE 40-50? n.d. 86 370 As
e
e
CANNIZZARITE 40-50? n.d. ? 288 767 Pb Bi S COSALITE 'V43 74-161 286 21b 767 Pb Bi See
CSIKLOV AITE 'V45 <100 ? 244 15a Bi Te SJOSEITE A& B
...
47.7-59.8 29-87 236 15a 437 Bi Te S Pb* Se* HEDLEYITE...
48.0-51.2 30-89 246 15a 436 Bi TeSTIBIOPALLADINITE 49.0-57.2 n.d. 324 19a b 413 Pd Sb ALLOPALLADIUM
...
'VSO 100-300? 322 19b 342 PdLAlT AKARITE
...
'VSO 36-50 228 433 Bi Se SPALLADIUMBISMUTHIDE
...
'V50.1 105-125 330 PdBi VOLYNSKITE 54.3-55.5 55-103 238 Ag Bi Te WEHRLITE ·'V55 'V81 238 15a 436 Bi Te MONTBRA YITE...
55.8-67.3 198-228 238 15b 432 Au Te Pb Bi ALLARGENTUM...
>60 143-157 82 407 Ag Sb IRiooSMIUM...
61.5-72.0 n.d . 334 19b 355 Os Ir INDIUM 90-95 130-159 104 Inee
SCHREIBERSITE...
n.d. n.d. 142 23 363 Fe Ni CoSTANNITE III n.d. n.d. 314 552 Cu Sn Ag S P Fe* Zn*
e
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NOVAKITE...
n.d . 387-398 ll2 398 Cu Ag AsTIN n.d. l(}·15 34 364 Sn
COHENITE n.d. n.d. 142 23 362 FeC Ni* Co·
ZINC n.d. 'VBO 74 365 Zn
ACHAVALITE n.d. n.d. 216 601 Fe Se
ADDITIONAL MINERALS (References see via 'index' in -Supplementary lists of minerals or on XRD cards)
SHADLUNITE 20.1-30.0 210 Fe Cu Pb Cd S MANGANESE-SHADLUNITE 22.7-33.8 195 Fe Cu Mn Pb Cd S
e
AKTASHITE 27.2-30.7 300-346 HgCu As Sb S UNNAMED Cu-Bi-SULFOSALT 32.8-32.1 n.d. Bi Cu Ni S GUSTAVITE 42-46 175-218 Bi Pb Ag S OSARSITE 45-49 n.d. Os AsS VINCENITE 51.7-56.0 494 Pd Pt As Sb Tee
MATIAGAMITE 52.7-53.1 383-404 Co Fe Te BOROVSKITE 53.3-61.2 88.3 Pd Sb Tee
POLARITE 56.8-61.2 168-232 PdPbBi KISBITE 58.8-59.6 420-513 Ni Sb TULAMEENITE 60.0-66.5 420-456 Pt Ir Fe Cue
SCHACHNERITE 72.2 n.d. AgHg P ARALSCHACHNERITE 70.9 n.d. AgHg CHILENITE 77-81 n.d. Ag Cu Bi MOOIHOEKITE n.d. 261 Cu Fe Se
HAYCOCKITE n.d. 263 Cu Fe S SCHNEIDERHOHNITE n.d. n.d. IR FeAsONore: Other new anisotropic (not specified) minerals
49 73 97 121 145 169 193
PROPERlY
Mineral isDISTINCTL Y ANISOTROPIC
(003)e
2 26 74 122 146 CRITERIA Under crossed, or nearly crossed, polars, the mineral shows a distinct brightening (generally with the colours white, yell ow
and orange) and four extenction positions within one revolution of the stage.
171 195 REMARKS - It is recommended that the strongest light avaiJable be used, with the diaphragms opened. 172 196
- The anisotropic brightening is a function of the section orientation. For determination of the degree of anisotropy it is the
-maximum brightening which is considered. 197
- Abundant internal reflections can mask the anisotropic brightening.
174 198 TYPICAL
EXAMPLES: CASSITERITE, CINNABAR, CHALCOCITE, COLUMBITE 175 199 176 200 OTHER DISTINCTL Y ANISOTROPIC MINERALS 201 Mineral Reflectanee VHN Internal References Composition
178 202
%
range reflection U+B Sch. RANIGERITE 7.2-8.2 1206-1561 210 Sn Mg Zn Fe Al 0 OH 11 35 59 107 131 155 179 203 HOGBOMITE 'VlO 1048-1214 IR 182 974 Fe Mg Al Fe Ti 0
STARINGITE 11.8-14.5 1033-1187 IR 208 Fe Mn Sn Ti Ta Nb 0
e
60 84 108 132 180 20<1 WODGINITE 13.9-15.8 766-1088 IR 200 Ta Nb Fe Mn Sn Zr 0 12 156
PLA TTNERITE 14.8-19.5 490-642 IR 162 7a 997 PbO
e
PSEUDOB ROOKITE 'V15 n.d. IR 178 7a 1024 FeTiO 13 37 85 109 133 157 181 205·
HYDROHETAEROLITE -> 15-20 n.d. IR 340 ZnMnO OH THOREAULITE -> 15.8-19.4 473-797 IR 200 Sn Ta Nb 0 62 86 110 134 158 182 206 Nb-RUTILE & -> 17.3-21.4 803-1239 ir 180 986 Fe Mn Nb Ta Ti 0 Ta-RUTILE QUENSELITE 17.8-20.8 153-186 IR 348 1b 20b c 944 Pb OMn OH 63 87 111 135 159 183 207 KARELIANITE -> 'V18 'V1790 212 945 VO o<-VREDENBURGITE 18-20 n.d. 346 20b c 920 Mn FeO 16 40 64 184 208' DONATHITE <20 n.d. 172 Fe Mn Zn Cr 0 MET ASTIBNITE 2 (}.40? n.d. IR 44 698 Sb S ESKEBORNITE -> 20.4-37.9 141-202 222 3d 16a 601 Cu Fe Se 17 41 65 185 209 HOCARTITE -> 22.4-24.8 n.d. 308 Ag Sn Fe S VRBAITE 26.2-36.4 n.d. IR 46 1b 723 Tl Hg Sb As S 18 90 186 210 RHODOSTANNITE 'V27.8 243-266 314 Cu Sn Fe S CHALCOTHALLITE 29.1-32.7 61-90 46 Cu Tl S SINNERITE 29.5-31.5 357-390 68 Cu As S 187 211 EUCAIRITE -> 'V30 23-94 224 4d 12e 16a 480 Cu Se Ag
e
JALPAITE !v30 23-30 38 8e 12e 482 Ag Cu S 164 212 HUTCHINSONITE -> 30.0-31.0 170-171 IR 298 9 12e 22a b 731 Tl Pb As S
FÜLOPPITE 30-35 n.d. 272 18 750 Pb Sb S 165
-
213 SEDERHOLMITE -> 3(}.35? n.d. 226 614 Ni Se NSUTITE -> 3(}.40 350-1288 358 1006 MnOOHe
HOROBETSUITE -> 30-50? n.d. 52 698 Bi Sb S 214 MARRITE 31.5-34.0 161-171 IR 298 734 Pb Ag As S PLAGIONITE 31.8-38.0 120-165 ir 276 18 781 Pb Sb S 167 191 215 DADSONITE 32.7-39.7 n.d. IR 272 Pb Sb S GRATONITE 33.4-34.4 123-156 ir 298 12a 22b 746 Pb As S LIVEINGITE 34.0-36.0 173-183 ir 300 Pb As S 168Mineral Refleetance VHN Internal Referenees Composition
%
range reflection U+B Seh RABAUMHAUERITE -+ 34.0-39.0 128-182 ir 300 22a 741 Pb As S Ag*Tl* VEENlTE 34.3-45.5 156-172 278 Pb Sb As S EMPRESSITE -+ 34.4-50.1 108-133 244 1015a 423 Ag Te BRAGGITE -+ 34.5-35.5 742-1030 330 19b 682 Pt Pd Ni S FREIESLEBENITE '\,35 85-140 264 14 733 Pb Ag Sb S SARTORITE 35.0-39.0 194-197 IR 302 22b 739 Pb As S Tl*
e
e
CASTAINGITE -+ 36-39 90-160 102 866 Cu Mo S Fe*Pb*Bi* SELIGMANNITE -+ 36.0-42.0 149-167 304 12d 22b 724 Pb Cu As Sb Seeee ee
BURSAITE 37.4-50.6 109-141 288 768 Pb Bi S TEALLITE 39.9-48.3 31-125 318 17 660 Pb Sn S SMITHITE 'V40 n.d. IR 266 715 AgAsS-
ee
TRECHMANNITE '\,40 n.d. IR 266 Ag As S BETEKHTINITE -+ 40-507 n.d. 94 481 Pb Cu Fe Se
e
NEYITE 40-507 n.d. 284 Pb Cu {\g Bi S BERRYITE -+ 41.8-43.0 131-171 284 Pb Cu Ag Bi S KOUTEKITE -+ 42-45 114-147 112 398 Cu As HERZENBERGITE -+ 42.1-44.3 48-114 ir 318 12e 17 659 Sn S SCHAPBACHITE -+ 42.6-45.3 59-91 282 21b 655 Ag Bi S VYSOTSKITE 'V45 n.d. 330 682 Pd Ni Pt S LILLIANITE 'V45 120-195 286 21b 769 Pb Bi S PAP AGUANAJUATITE '\,45 30-160 228 12e 16a 702 Bi Se S BONCHEVITE -+ 45.8-46.6 129-205 288 Pb Bi S FERROSELITE -+ 47-50 700-933 228 Fe Se Coe
KOSTOVITE 49.3-60.1 35-43 250 427 Au Cu Te IKUNIOLITE -+ '\,50 n.d. 230 433 Bi S See
KITKAITE 52.0-62.3 109-119 248 420 Ni Te Se MONCHEITE -+ 52.7-58.8 n.d. 332 825 Pt Pd Te Bi KOTULSKITE -+ 53.0-67.9 '\,236 332 825 Pd Te Biee
MELONITE 54.5-66.9 63-156 252 15b 419 Ni Te MERENSKYITE -+ 60.9-67.4 n.d. 332 825 Pd Pt Te Bi ALGODONITE -+ '\,61.5 217-255 114 6b 114 Cu As PARATENORITE -+ n.d. n.d. 118 CUOe
ee ee
ADDITIONAL MINERALS (Referenees see via 'index' in supplementary lists of minerals or on XRD eard)BUKOVITE 26.8-30.2 61 Cu Tl Fe Se HODRUSHITE 32.0-33.4 187-213 Cu Bi Fe S PAOLOVITE 41.8-56.0 360-400 Pd Sn
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e
OSARSITE 45-49 n.d. Os As S KAWAZULITE 45-50 n.d. Bi Te See
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LANGISITE 45-4-51.0 780-857 Co Ni As ATHENEITE 47.47-59.95 419-442 Pd Hg As UNNAMED Cu (Sn, Sb) 47.3-68.6 n.d. Cu Sn Sbee
STUMPFLITE 52.0-64.5 385 Pt Sb Bi POLARITE 56.8-61.2 168-232 Pb Pd Bi TELLURANTIMONY 63.7-65.1 40.2-73.9 Sb Bi Te TAKANELITE n.d. 480 Mn Ca Mg Mn 0 H20 UNNAMED MoS, n.d. n.d. n.d. Mo S UNNAMED Pb Bi n.d. n.d. n.d. Pb Bi Te S Telluride-SulfideNore: Other new anisotropic (not specified) minerals
r
25 49 73 169 193PROPERTY
Mineral is
STRONGL Y ANISOTROPIC
(004)2 26 74 170 194
CRITERIA Under crossed, or nearly crossed, polars, the mineral shows bright and vivid colours of high intensity and four well-defmed
extinction positions within one revolution of the stage. 3 27 51 75 195
REMARKS The colours are visible with a lower illuminating intensity than is the case with minerals having a we aker anisotropy. 4 28 52 76 196 - The anisotropy is a function of the section orientation. Some sections can show a we aker brightening, or remain dark 5 29 53 173 197
during rotation of the stage.
Vivid colours are also shown by highly reflecting minerals who se anisotropy is only weak or distinct. The observed 6 30 54 174 198
-anisotropic brightening must always be related to the mineral's reflectance.
7 31 175 199
- Take care wh en estimating the anisotropy of a mineral in a fine-grained aggregate. The anisotropy is orten masked by the random orientation and its degree underestimated.
176 200
TYPICAL
EXAMPLES: ARSENOPYRITE, BISMUTH, CUPRITE, ILMENITE, MARCASITE, PYROLUSITE 129 153 201
130 154 178 202
OTHER STRONGL Y ANISOTROPIC MINERALS
11 35 59 131 155 179 203
Mineral Reflec tance VHN Internal References Composition
%
range reflection U+B Sch RA 1236 60 B4 108 132 156 180 204 AURORITE 9-30? n.d. 344 Ag Ba CaMn 0 OH GAUDEFROYITE 10.1-13.5 "-'840 IR 338 Ca Mn BCO OH 13 37 61 181 205 GIEKlELITE 11.6-14.9 560-930 IR 176 7c 974 Mg Ti 0 Fe RANCIEITE 12.5-15.0 n.d. 338 Fe Mg Mn Ca 0 OH 14 38 62 182 206
TIN-T ANT ALITE 14.8-15.9 "-'660 IR 200 Mn Ta Nb Sn 0 TAPIOLITFrMOSSITE 14.9-17.8 796-1132 ir 202 1019 Fe Mn Ta Nb 0 MAROKITE 16.1-19.4 "-'800 IR 340 CaMnO 39 63 183 207 LITHARGITE "-'20 n.d. IR 50 PbO STANNITE JAUNE 20.0-31.9 n.d. 310 Cu Sn Fe S 16 40 64 184 208' STANNOIDITE 20.6-29.6 232-271 310 Cu Sn Fe Zn S RAGUINITE 24.9-40.6 n.d. 46 Tl Fe S 17 41 185 209 OTTEMANITE "-'30 n.d. IR 316 Sn S ARAMAYOITE 30-35 n.d. ir 264 14 21a b 654 Ag Sb Bi S MCKINSTR YITE 30-35 "-'60 44 Cu Ag S 18 66 186 210 CUPROBISMUTITE 30-50 n.d. 294 707 Cu Bi S LORANDITE 31.4-32.6 39-57 IR 44 8b 722 Tl As S 19 43 67 91 115 139 163 187 211 GUETTARDITE 32.2-44.2 180-197 274 PbSbAsS STERRYITE 33.9-40.4 n.d. 278 PbSbAsS PLA YF AIRITE 34.0-42.3 150-171 276 Pb Sb As S 20 6B 140 188 212 SORBYITE 34-45 172-186 276 PbSbAsS TWINNITE 34.6-45.6 131-152 278 Pb Sb As S 21 69 141 189 213 LAUNAYITE 35.5-46.2 171-197 274 Pb Sb As S GUDMUNDITE 36-58 402-1221 130 13b 858 Fe Sb S DUFRENOYSITE 36.5-40.5 145-156 ir 302 22b 743 Pb As S 22 70 STUETZITE 36.7-38.9 75-90 242 10 15a 423 Ag Te MADOCITE 37.9-44.5 141-171 274 Pb Sb As S 23 71 95 119 PLATYNITE "-'40 n.d. 228 665 Pb Bi Se S PAXITE 40-50? n.d. 112 ARSENOLAMPRITE 40-50? n.d. 86 370 Cu As As 24 48 72 96 120
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Mineral BENJAMINITE USTARASITE PAVONITE TELLURIUM FROHBERGITE ARGYROPYRITE FROODITE GUANAJUATITE OSMIUM IRIDOSMIUM NOLANITE MONTROSEITE HASTITE WILKMANITE FREBOLDITE MÄKINENITE Reflectance % 41-43 'V42 'V42 43.4-53.5 44.6-50.9 'V45 'V50 'V55 58.5-65.6 61.5-72.0 n.d. n.d. n.d. n.d. n.d. n.d. VHN range 179-194 n.d. 100-300? 25-87 250-297 n.d. n.d. 42-210 n.d. n.d. 717-766 266-300 n.d. n.d. n.d. n.d. Internal reflection U+B 284 290 282 246 244 268 330 230 334 334 192 100 226 224 226 226 References Sch. 21a 15a 15a 3d 14 19bADDITIONAL MINERALS (References see via 'index' in supplementary lists of mineraIs or on XRD card) TOCHILINITE RASVUMITE PERMINGEATITE PICOTPAULITE UNNAMED Ag Sb Te S UNNAMED HEXAGONAL CU1.83S HEYROVSKYITE OOSTERBOSCHITE UNNAMED CuO 12Fe094S STANNOP ALLÄDlNITE UNNAMED Cu (Sn, Sb) PLUMBOP ALLADINITE UNNAMED Bi-Pd Min. HAAPALAITE UNNAMEDSULFOSALTS 8.0-20.2 14.0-32.3 24.2-31.5 24.3-33.7 26.1-37.6 'V35 39.6-47.3 40.9-48.1 41-48.5 45.0-50.0 47.3-68.6 49.5-62.6 n.d. n.d. n.d. Nore: Other new anisotropic (not specified) minerals
see Table on Porperty Card 005
15.0-48.8 24.3-43.3 'V234 41 n.d. n.d. 'V50 166-234 'V340 32.75 387-452 n.d. 407-441 105-125 9-11 n.d. n.d. RA 737 704 383 845 628 813 702 355 832 692 603 619 Composition Pb Ag Cu Br S Pb Bi Sb S Ag Bi S
Te Se* Au* Ag* Fe* Fe Te Ag Fe S Pd Bi Bi Se S Os Pt Os Ir V Fe Al Ti 0 V FeO OH Co Se Fe Ni Se Co Se Ni Se Fe SMgOH K Fe Mg S Cu Sb As Se Ag Sb Te S CuS Pb S Bi Pd Cu Se Cu Fe S Pd Sn Cu Sn Sb Pd Ag Pb Bi Sb Sn Cu Pb Bi Fe Ni S MgOH Cu Bi Pb S
