However, it is thought to represent a rock intermediate between high-grade metamorphism and melting. Thought to be derived by metamorphism of a quartz sandstone or chert. Involves a large-scale addition of Al and Si. Greisen - granoblastic aggregate of quartz and muscovite with accessory topaz, tourmaline, fluorite, rutile, cassiterite and wolframite. Granofels - granulite facies metamorphic rock dominated by equant grains of quartz, K feldspar, pyroxene and garnet.
All minerals are anhydrous and the texture is granoblastic.
Characteristic is the presence of pyroxene. Associated with gabbroic intrusions. Greenstone - aphanitic weakly metamorphosed mafic igneous rock with a basaltic protolith. Dominated by epidote, chlorite, actinolite and carbonates. Na amphibole and rock becomes an amphibolite.