migmatite gneiss - a gneiss that shows remelting, from India - display specimen

Migmatites form by the partial melting of gneisses.  Lighter-colored silica-rich crystalline bands, called leucosomes, are compositionally similar to granite and represent partial melting and segregation of the granitic melt. The darker biotite and hornblende-rich bands, called melanosomes, with higher melting points, are unmelted and preserve the original metamorphic texture of the gneiss, so this rock straddles the boundary between metamorphic and igneous realms. The chemical composition of migmatites is highly variable, and specific details depend on the geological context, the parent rock, and the metamorphic conditions. 

This Precambrian migmatite, with a granitic parent, comes from a quarry in India, near the village of Chendrapalli, Krishnagiri District, East Ghats, in the state of Tamil Nadu. There, large blocks of this colorful rock are quarried, slabbed and polished and sold as a decorative stone.

This specimen is polished on one side. The pencil is 5 1/2" long, for scale.

This specimen is on hold for a college and is not available.

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