The orthoclase-microcline inversion

Abstract

The association of orthoclase and microcline in the same rock has been commented on by many writers, and from these occurrences attempts have been made to deduce the relative stability of these two low-temperature forms of potash-felspar. Ahnost all investigators have concluded that nlicrocline is the lower-temperature modification, but difficulties in explaining the relationship of adutaria to orthoclase and microcline have been encountered. The identification of the monoclinie potash-felspar in association with microcline is almost always based on optical properties, viz. straight extinction in the zone [010] or the absence of visible multiple twinning.