Gageite Locality: N'Chwaning II Mine, N'Chwaning Mines, Kuruman , Kalahari manganese fields, Northern Cape Province , South Africa ( Locality at mindat.org ) Greyish-white fibrous Gageite on Rhodochrosite. Field of view 7 mm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Gageite
Gageite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₂₁Si₈O₂₇(OH)₂₀.
It crystallizes in the orthorhombic crystal system (space group Pnnm).
Key properties: Mohs hardness 3; specific gravity 3.46–3.58; Highly vitreous luster; optically biaxial.
IMA symbol Gge, grandfathered status — known before the IMA’s founding, named in 1910.
A late-stage low- to medium-temperature mineral, implanted on other species in fissures and solution cavities, in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA).
It is found associated with Zincite, willemite, pyrochroite, leucophoenicite, calcite, chlorophoenicite (Franklin, New Jersey, USA); leucophoenicite, hausmannite, rhodochrosite.
The name refers to Robert B. Gage, of Trenton, New Jersey, USA, who analyzed the first specimens.