Moonstone originates from the orthoclase feldspar mineral family.
Moonstone is a mix of layers of albite and orthoclase.
Thus, for instance, near Nikko in the upper valley of the Daiya-gawa, and in several other places in the neighboring mountains, a granite-porphyry appears with large, pale, flesh-colored crystals of orthoclase, dull triclinic feispar, quartz and hornblende.
In point of absolute mass they are insignificant compared with the abundance and variety of potassiferous silicates, which occur everywhere in the earth's crust; orthoclase (potash felspar) and potash mica may be quoted as prominent examples.
Like the highlands of eastern Asia, those of Turkestan are mostly built up on Pre-Cambrian gneisses and metamorphic slates, resting upon granites, syenites, old orthoclase porphyries, and the like.