- Baltic Brown
Rapakivi granite from the Precambrian of Finland. Baltic Brown Granite is a variety of rapakivi granite called wiborgite, characterized by having large K-feldspar spheroids rimmed (usually) by greenish plagioclase feldspar. Wiborgite is composed of K-feldspar, plagioclase feldspar, quartz, biotite mica, and hornblende amphibole. This rock comes from the Wiborg Batholith (a.k.a. Wiborg Rapakivi Granite Batholith, Wiborg Massif, Vyborg Batholith) in the Baltic Shield (Fennoscandian Shield).