Sillimanite

The sillimanite in this specimen, from Sterling Hill, occurs as tiny (1-3 mm), slender, prismatic crystals within grains of pink almandine in a pale gray, quartz-oligoclase-almandine gneiss with saccharoidal texture. Small scales of a brown mica are present throughout but are widely scattered. The sillimanite is neither abundant nor conspicuous but is obvious upon hand-lens inspection of the garnet grains (see photo SIL6b). This specimen, FMM-1964 of the Franklin Mineral Museum, at one time was in the collection of Ewald Gerstmann. The Gerstmann collection was later purchased by Art and Harriet Mitteldorf, who in 1985 donated it to the Franklin Mineral Museum.

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