Pink holdenite and orange kolicite crystals from the type locality for both species in Sterling Hill. Specimen found in 1979. — Photo: David Hospital · CC BY-SA 4.0
Holdenite
Holdenite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₆Zn₃(AsO₄)₂(SiO₄)(OH)₈.
It crystallizes in the orthorhombic crystal system (space group Abma).
Key properties: Mohs hardness 4.5; specific gravity 4.11; typically red or orange; white streak; Vitreous luster; optically biaxial.
IMA symbol Hde, grandfathered status — known before the IMA’s founding, named in 1927.
Found as a secondary mineral in veinlets, on slip surfaces, and as interstitial fillings within a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA).
It is found associated with Franklinite, willemite, pyrochroite, barite, kolicite, sussexite, kraisslite, zincite, sphalerite, galena, calcite, rhodochrosite.
The name refers to the mining engineer Albert Fairchild Holden (1866–1913), of Salt Lake City, Utah, USA, in whose collection the mineral was first noticed.
Collections: Collector Favorites, Rare & Remarkable.