Description
Every mineral is a story of chemistry, pressure, and patience. Sillimanite is one of three aluminum silicate polymorphs (kyanite and andalusite being the others), each stable at different temperature-pressure conditions. Fibrous sillimanite — ‘fibrolite’ — indicates high-grade metamorphism. Delaware’s state mineral, it was first described from these very outcrops in 1824.
This specimen originates from Brandywine Summit, Delaware, USA, one of the world’s most significant localities for this type of material. Collectors and scientists have drawn from this region for generations, and for good reason: the combination of geological conditions here produces specimens of exceptional quality and clarity.
Every specimen is unique. Photographs approximate the visual experience, but the real thing — its weight, its luster under a raking light, the way it catches the corner of your eye — can only be experienced directly.
