mica schist, micaceous schist, micas late

Geol. & Petrol.: A slaty metamorphic rock com. posed of mica and quartz. The mica is usually muscovite (potash mica), though sometimes it is biolite (magnesian mica). The rock usually splits along the micaceous folia. Occasionally mica seems to constitute the whole ma of the rock. Next to gnei , mica-schist is the most common metamorphic rock. It sometimes pa es gradually into others of the same series. The addition of felspar making it become gnei , and a decrease in the amount of quartz with an increase of chlorite makes it chlorite schist. Sorby has seen traces of ripple rocks. Various imbedded minerals occur, as quartz, garnet, . IMG:content-1179.png:[blocks in formation] Min .: A variety of hæmatite (q. v.), occurring in thin tables or as aggregated folia, mica-like.