Fig. 5
Bristen granite photomicrographs: a Primary igneous biotite partly replaced by muscovite and opaques. Dark areas and black spots within the pseudomorph are additional replacement minerals, including ilmenite, magnetite, sulfides, various niobates, and others. b Same as a with crossed polars, c Fractured feldspar and quartz matrix with carbonate and accessory minerals in small fractures, d Primary igneous overgrown with chlorite and stilpnomelane