Figure 10.--Photomicrographs of plutonic and metamorphic rock fragments, granule size, Minturn Formation: A) sample 31M, 665 m below top, Minturn Formation, Eureka Mountain section; and B) sample 349 (not analyzed), about 1080 m below top, Minturn Formation, near Eureka Mountain section. (A) and (B), taken under plain polarized light, correspond to (C) and (D), respectively, taken under cross-polarized light. Potassium feldspar stained yellow by cobaltinitrite. QMS, quartz mica schist; QP, quartz-plagioclase plutonic rock; Q, monocrystalline quartz; K, potassium feldspar; P, plagioclase; CP, compound plagioclase grain; and M, mica (biotite marked but muscovite also present).