QuartzFeldsparPorphyry (Graniphyro LiparoseAlaskose ...
QUARTZFELDSPARPORPHYRY FROM LLANO, TEX. 227 The feldspar phenocrysts are microcline, with extremely minute and regular multiple twinning in two directions. The delicacy of the twinning suggests a possible soda content in the potash feldspar approaching soda microcline. There is also a perthitic inclusion of