Journal of Petrology | Volume 43 | Number 3 | Pages 579-580 | 2002
© Oxford University Press 2002
BOOK REVIEW |
Optical Crystallography, by F. Donald Bloss. Mineralogical Society of America Monograph Series, No. 5., 1999 ISBN 0939950499. $32 ($24 for members). Hardback.
Nowadays, with so much petrological and mineralogical research carried out on polished material, using atomic number contrast (back-scattered electron) imaging on a scanning electron microscope–energy-dispersive system or microprobe, the publication of Donald Bloss’ book is a timely reminder that the fundamental tool for mineral identification is still the polarizing light microscope (PLM), particularly at the undergraduate level.
Optical Crystallography is an updated version of Bloss (1961)
, and retains much of the 1961 version with the addition of new material, particularly on the use of the spindle stage.
As implied by the title, this book is a comprehensive exposition of the theory and application of PLM techniques in determining the optical properties of crystalline material. The theoretical treatment has significantly more depth than that found in most reference works on mineral identification, especially those aimed at the undergraduate market. This is a handbook that is clearly directed at a broad audience of research workers who may use optical microscopy, from earth scientists to forensic scientists, ceramists, crystallographers and even pharmaceutical chemists.
The emphasis throughout is on the accurate measurement of optical properties (
, ß, 
, 2V, etc.). The chapters on the optical examination of isotropic substances (Chapter 5—which includes a discussion of the Becke line), the interference of light (Chapter 7), the optical examination of uniaxial crystals (Chapter 8), and the optical examination of biaxial crystals (Chapter 11) are excellent and the procedures for determining optical sign, refractive index and 2V are clear, thorough and illustrated with excellent line drawings.
As Bloss indicates in his preface, the text is designed ‘to give a firm foundation ... for petrographic studies’ (my italics). What it does not do is provide any systematic lists or descriptions of the optical properties of individual minerals as an aid to identification. The only concession Bloss makes to mineral identification is to provide an augmented Michel–Levy birefringence chart, and, buried away on page 119, the citations to four standard reference books. The author also recommends the use of the MinIdent computer database (Smith, 1992). However, this commercial DOS-based package was apparently last updated in 1996 (see http://www.compusmart.ab.ca/micronex/products.htm), and there are several free comprehensive and regularly updated mineral database Internet sites that were extant when the book was published to which the reader could also have been directed (e.g. David Barthelmy’s site at http://webmineral.com/). Despite this, there is a whole chapter devoted to the identification of asbestos fibers (Chapter 13), which could have been written as a case study on the practical application of optical techniques, but as it stands is of interest only to environmental health scientists.
My biggest criticism is the emphasis placed on the use of the spindle stage (Chapter 9 for uniaxal minerals, Chapter 12 for biaxial ones). Perhaps this emphasis is not surprising, given Professor Bloss’ pioneering and preeminent work both as a microscopist and in the use of the spindle stage. However, there is no chapter, section (not even a listing in the index) that describes or discusses the use of the universal stage—it is as if the universal stage did not exist as a major microscopy tool for petrographic and microstructural studies of minerals in the context of their host rock. Although acknowledging that the spindle stage is of immense value for its ease of use and versatility in single-crystal work, this lack of any consideration of the universal stage is a significant weakness.
It always seems a little churlish for a reviewer to highlight mistakes or instances of inadequate proof reading. But there are a number. There is at least one reference not listed in the bibliography (McCrone, 1992), and in the introduction to Chapter 9 there are four authors cited without dates, and, from the same paragraph, it would appear that 1950 represents the date of a recent revival in the use of the single-axis stage! Elsewhere, lines of text are duplicated and there are typographical errors in the annotations to the Michel–Levy chart (Figure 8-13). In this figure the thin-section thickness is marked as being in nanometers (nm), when it is clearly in millimeters, quartz is given a 
value of 0·007 instead of 0·009, and there is no radial line of equal retardation equal to 0·009 marked on the chart, despite this being specifically discussed in the figure caption.
So, Optical Crystallography is a valuable if somewhat idiosyncratic (the reader is referred to the Applications section of Chapter 12 to understand this comment) reference tool for microscopists.
E. Condliffe
School of Earth Sciences, University of Leeds
REFERENCES
Bloss, F. D. (1961) An Introduction to the Methods of Optical Crystallography. New York: Holt, Rinehart and Winston, 294 pp.
Smith, D. G. W. (1992) Computer-assisted mineral identification using conventional optical observations. Microscope 40, 39– 58.
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