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Description

The study of opaque minerals or synthetic solids in polished section using the polarizing reflected-light microscope is the most important technique for the identification and characterization of the opaque phases in a sample and the textural relationships between them. Since most metalliferous ores are comprised of opaque minerals, this study has been traditionally known as ore microscopy and has found its greatest applications in the study of mineral deposits. It may be applied, however, as a general technique in the study of igneous, sedimentary, or metamorphic rocks containing opaque minerals and even in the study of metallurgical products or other synthetic materials. The objective of this text is to present an up-to-date introduction to ore microscopy for the student or professional scientist who is unfamiliar with the technique-an introduction that would accompany a course at the senior undergraduate or graduate level or that would provide the professional with a first step in familiarization. No attempt has been made at a comprehensive treatment of the subject; for this the reader is referred to the excellent works of such authors as Rarndohr, Uytenbogaart and Burke, Galopin and Henry cited in relevant sections ofthis text. Emphasis is placed on the basic skills required for the study of opaque minerals in polished section, and information in the text and appendices on the more common ore minerals and assemblages provides examples.

The first two chapters cover the design and operation of the ore microscope and the preparation of polished (and polished thin) sections. A chapter dealing with qualitative mineral properties used in identification is followed by a discussion of reflected-light optics. The quantitative measurement of reflectance, color, and microhardness are treated in Chapters 5 and 6 along with overall schemes for employing these measurements in identification. Chapters 7 and 8 deal with ore mineral textures and paragenesis, and include a brief discussion of the study of fluid inclusions. Chapters 9 and 10 are concise discussions of many of the major ore mineral associations observed under the microscope. These discussions are not intended to be exhaustive, especially with regard to comments made on the genesis of the ores, but are designed to aid understanding by placing the ore mineral textures and associations in a broader geological context. Chapter 11 deals with the applications of ore microscopy in mineral technology. The appendices contain the data necessary to identify approximately 100 of the more common ore minerals-those likely to be encountered by the student in an introductory course andthose frequently encountered by the professional scientist. Key references to more detailed accounts are provided throughout the text. The dependence ofthe properties, textures, and associations of the minerals on their crystal chemistry, thermochemistry, and phase relations is an aspect of modern studies of ore minerals that is particularly emphasized.

This second edition retains the overall structure of the first edition. Chapters 1and 2, dealing with the ore microscope and with the preparation of samples for ore microscopy, have been updated and revised to take account of technical developments. Chapters 3 and 4 deal with qualitative methods of mineral identification and with reflected light optics, and remain largely unchanged. Chapters 5 and 6 deal with quantitative methods in reflected-light microscopy and have been revised to include new technical developments and advances in theory. Chapters 7 and 8, dealing with ore mineral textures, paragenesis, formation conditions, and fluid inclusions, incorporate new data and examples. Chapters 9 and 10, which cover the most important examples of ore mineral assemblages, have been rewritten so as to incorporate many new references to original studies that have been performed in the years since the publication of the first edition. Developments have also taken place in the applications of ore microscopy in mineral technology and in the study of both the products of milling and concentration of ores,and the synthetic analogs of minerals that occur in metallurgical, corrosion, and waste products.

As in the first edition, an important feature of this text is the incorporation of appendices detailing and tabulating the diagnostic properties of about 100 ofthe most common ore minerals. These data tabulations have been updated using the most recently available quantitative data. Another appendix, which briefly describes ancillary techniques for the study of ore minerals, has been extended to include the most recent innovations.

James R. Craig, Blacksburg, Virginia
David J. Vaughan, Manchester, England
November 1994

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