Fig. 32.-Biotite (Bi₁) is transformed to muscovite (Ms ₁ double prime)

A---Muscovite (Ms₁ double prime) is colorless and transparent in biotite (Bi₁) in plane-polarized light. B---Ms ₁ double prime is different from Bi ₁ in interference color in crossed polars. Also, nibble replacement muscovite grains (Ms ₁ single prime and Ms ₂ single prime) occur at the contact between Bi₁ and Bi₂. Baimianshi granite, Huichang County, Jiangxi Province.