Sillimanite

Abundant, pale greenish yellow, bladed, tapering crystals of sillimanite, most 1-2.5 cm long and in rough alignment, in feldspar-quartz-magnetite gneiss with minor apatite. This example is from the collection of Joe Orosz, former curator of the Franklin Mineral Museum, and almost certainly was collected by him during one of his visits to the Edison mines. It was donated to the FMM by his widow, Sharon Orosz, in late 2017, and assigned catalog number FMM-7988. As noted by Dunn (1995), sillimanite from this area was “used to establish the granulite facies degree of regional metamorphism” of the local Proterozoic rock units.

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