Introduction to Optical Mineralogy and Petrography

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Following Iddings, Winchell, and other American petrographers, the symbols X, Y, and Z, are here em ployed in referring to the axes of ether elasticity, instead of the German a, b, and c, used in many text and refer ence books. This is done to avoid confusion, especially in conversation or discussion, with the crystallographic axes.