Stable mineral assemblages of igneous rocks . A. Rittmann, 1973. Springer, Berlin, 262 pp., D.M. 76.00

Abstract

Rocks can be named, described and compared in terms of their chemical analysis, or in terms of their actual mineral content measured in volume per cent (the "mode"). Both are of course related, although similar chemical compositions may lead to widely varying modes depending on subtle changes of temperature, pressure, fluid pressure of various volatiles, content of rare elements, rate of cooling etc. This book contains interesting examples. Although the book covers both rock groups, the author mainly concentrates on volcanic rocks. He chooses for Streckeisen's classification system based on mineral content, while acknowledging that the groundmass of these rocks is often difficult to determine, or even glassy. Yet, the better approximations made possible by Burri's (1959, 1964) norm calculations are not treated, his book is not even in the references. A more fundamental criticism is that the great majority of the volcanic rocks are unstable mineral assemblages, and thus are not covered by the title of the book. Rittmann's method seems to imply a lot of work. The enormous number of symbols or calculation values (table 21 listing 50of them is not exhaustive) further adds to its opacity. It will receive less acceptance than the CIPW system "mainly because the actual meaning of those symbols remain(s) incomprehensible to an ordinary earth-scientist who is not a specialist in calculating and using such symbols" )p.7).