Ž .Lithos 59 2001 151–152www.elsevier.comrlocaterlithos

Book review

Optical Crystallographyby F. Donald Bloss, Mineralogical Society of Amer-ica, Washington D.C., USA, 1999. Hardcover, Xq239 pp. US$ 32.00, ISBN 0-939950-49-9

A thorough knowledge of optical crystallographyis immensely useful to geologists and materials sci-entists. It constitutes the basis for work with thepolarizing light microscope, which—as ProfessorBloss states in the preface—isAthe premier tool forrapidly identifying the minerals and the mineral reac-tions that occur in petrographic thin sections ofrocksB and—also—has beenAquintessential for de-termination of single crystals and fragments thereofB.The present textbook has a predecessor in F. DonaldBloss’ earlier classicAn Introduction to the Methods

( )of Optical Crystallography 1961 and contains top-ics of another one of his major books:The Spindle

( )Stage: Principles and Practice 1981 .Optical Crystallography is arranged in 13 chap-

ters. The first four, fairly short chapters deal with thegeneral physics of light and its behaviour in isotropicmedia and with the polarizing light microscope.Chapter 5 describes the optical examination of trans-parent isotropic solids, shows how to measure refrac-tive indices by immersion methods, and explains, indetail, principle and practice of dispersion staining.This technique can be of great help withAneedle-in-the-haystack searchesB for minor components insamples with many different mineral grains.

Chapters 6 and 7 present the concept of theoptical indicatrix and explain double refraction and

Žinterference phenomena interference colours, inter-.ference figures . Chapter 8 applies these principles to

the optical examination of uniaxial crystals, and isfollowed by a first introduction to the detent spindlestage invented by F.D. Bloss some 30 years ago. The

spindle stage is an ingeniously simple and inexpen-sive accessory to the polarizing microscope. It en-ables the fast and elegant determination of the princi-pal indices of refraction of single grains. Chapter 9presents this method by example of uniaxial crystals.

Chapters 10 to 12 are devoted to an in-depthtreatment of biaxial crystals, their optical examina-tion, and spindle stage study. First, a clear presenta-tion is given of the biaxial indicatrix and the geomet-ric relationships between wave normals, vibrationdirections and ray paths. This is followed by thedidactic explanation of biaxial interference figures:how they are produced and how they can be recog-nized and interpreted. Chapter 12 demonstrates theuse of the spindle stage technique for investigationof optically biaxial solids. In combination with Bloss’computer programme EXCALIBR, the spindle stagemakes it possible to quickly orient biaxial crystals,and to determine their refractive indices and the axialangle Awith unprecedented accurracyB. The axialangle 2V is most sensitive to slight changes in acrystal’s chemistry and atomic structure, and there-fore, suitable to monitor small compositional varia-tions. Despite its promising range of possible appli-cations, this method is not much used outside thetraditional mineralogy. The development is headingtowards the automation of refractive index determi-nations. This would permit rapid, precise, and accu-rate measurements, thus providingAnew impetus forthe optical study of minerals and organic crystalsŽ .including drugs , and for their study in forensic

wmineralogy. What could be more convincing than tofind, in a soil or sand associated with a suspect,

Ž .biaxial grains with the same 2V and dispersion asx Ž .those occuring at the site of the crime?B p. 198 .

The book is rounded off by a chapter on the rapidoptical identification of asbestos fibers by dispersionstaining, includes determinative tables and contains

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valuable practical hints on sample preparation andchoice of immersion liquids and the measuring of afiber’s refractive indices.

The book also includes an interference colourchart, a useful bibliography, an appendix with datafor immersion liquids and—in some chapters—read-ing lists, plus problems and review questions. Thepoems Light Reflexions and The Isogyre add a hu-merous touch, and the picture on the front covershows that there is a decidedly aesthetic side tocrystal optics. The image represents a multiple-ex-posure photomicrograph of blue and yellow-orangebeams. They form a beautiful radial pattern and areproduced by dispersion staining of an asbestos fiber.

The book’s structure proves very workable. Laterchapters build on early theoretical material, but, withsome previous knowledge of the subject, variousparts and chapters can be read independently. Astrong asset in that sense are the extended summa-ries at the beginning of each chapter. They representexcellent short versions of the chapters, making reca-pitulation really easy. All parts of the text are care-fully illustrated. Pleasantly detailed captions accom-pany the 175 figures, so that these can be studied,largely without returning to the main text. The book

Žis well written, the style is clear and easy to read as.much as the dry and technical subject permits .

Optical Crystallography is a classical and moderntextbook at the same time. The topics are presentedsystematically and thoroughly, covering the widerange from optical crystallography proper to com-

puter-assisted mineral identification of microscopi-cally small, single grains. The book imparts allnecessary theoretical background for understandingcrystal optical phenomena seen under the polarizingmicroscope and, furthermore, provides a wealth ofinformation on useful methods and tricks of thetrade, some of which stem from the pre-microprobeera, and could easily fall into oblivion, if not pre-served in such books.Optical Crystallography is ahighly practical book ranging from the description ofclassical techniques to hints to pertinent web sites.

All in all, this is quite a fine book. I highlyrecommend it to all geologists studying minerals androcks and working with the polarizing microscope,and to material scientists interested in the identifica-tion of solids.Optical Crystallography makes for agood textbook for upper undergraduates and gradu-ates. As it requires an elementary knowledge incrystallography, it appears less suited for lower lev-els.

Hans Dieter Zimmermann)

Department of Earth Sciences,Aarhus UniÕersity,˚DK-8000 Arhus C, Denmark

E-mail address: geolhans@aau.dk

) Tel.: q45-8942-2509; fax:q45-8942-2525.