Kerimasite

kerimasite

fluorapatite

magnesioferrite

monticellite

Images

Formula: Ca3Zr2(SiFe3+2)O12
Nesosilicate (insular SiO4 groups), schorlomite group, garnet supergroup, zirconium-bearing mineral
Crystal System: Isometric
Specific gravity: 4.105 calculated
Hardness: 7
Colour: Light to dark brown
Environments

Carbonatites
Metamorphic environments

Localities

At Zlatno, Vysoká, Banská Štiavnica District, Banská Bystrica Region, Slovakia, kerimasite has been identified in association with andradite, grossular and their hydrated analogues, monticellite, perovskite, clintonite, anhydrite, hydroxylellestadite fluorellestadite, spinel, magnetite, brucite, valleriite and other minerals from a Ca-Mg skarn in the exocontact (on the skarn side of the contact) of a granodiorite porphyry intrusion in a Cu-Au skarn porphyry deposit. Kerimasite forms euhedral-to-anhedral crystals, 2 to 100 microns across. The crystals commonly show regular, oscillatory concentric zoning.
Kerimasite and associated skarn minerals originated during contact thermal metamorphism at temperature ~700oC and pressure ~70 MPa (0.7 kbar) (MM 79.3.715-733).

At the type locality, the Kerimasi volcano, Monduli District, Arusha Region, Tanzania, Kerimasite occurs as subhedral crystals up to 100 microns in size in calcite carbonatites, and as euhedral to subhedral crystals up to 180 microns in size in carbonatite eluvium. Kerimasite is light to dark brown in colour and transparent with a vitreous lustre. No cleavage or parting was observed and the mineral is brittle (MM 74.5.803-820).
Associated minerals include calcite, and rarely fluorapatite and magnesioferrite (HOM).

At Magnet Cove, Hot Spring County, Arkansas, USA, kerimasite has been found with perovskite (Mindat photo).
Kerimasite from Magnet Cove - Image

Back to Minerals