Willemite, Franklinite & Uraninite

Specimen Origin: Sterling Hill Mine (Franklin, New Jersey, USA)

The Sterling Hill Mine in Franklin, New Jersey, is one of the world’s most famous zinc ore localities and part of the renowned Franklin–Sterling Hill mineral district. This mine produced an extraordinary array of minerals, with more than 350 species documented, many of them fluorescent or unique to the locality. Willemite, franklinite, and uraninite are among the classic species from Sterling Hill, occurring together in the complex zinc-iron-manganese ores. Specimens showing this association are especially prized for their rarity, historic provenance, and striking visual and fluorescent qualities.

Willemite, Franklinite & Uraninite

Willemite is a zinc silicate (Zn₂SiO₄), often green to brown, strongly fluorescent in bright green under UV light. Franklinite is an iron-manganese zinc oxide (ZnFe₂O₄–Mn), usually black and metallic, occurring as octahedral crystals or massive ore. Uraninite, a uranium oxide (UO₂ to U₃O₈), appears black and massive, is strongly radioactive, and serves as a primary uranium ore. Together, these minerals from Sterling Hill represent the geological and mineralogical richness that makes this district a cornerstone of North American mineralogy.