Spinel , Calzirtite Dimensions: 1 cm × 0.4 cm × 1 cm Locality: San Vito Quarry, San Vito, Ercolano, Mount Somma, Somma-Vesuvius Complex, Naples, Campania, Italy Description: Dark spinel octahedra formed by numerous octahedra of microscopic dimensions, with small complex orange crystals of Calzirtite, in a metamorphosed matrix. Photo and sample by Imma Punzo. — Photo: Imma Punzo · Public domain
Calzirtite
Calzirtite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ca₂Zr₅Ti₂O₁₆.
It crystallizes in the tetragonal crystal system (space group I4_1/acd). It is a member of the Calzirtite structural group.
Key properties: Mohs hardness 6–7; specific gravity 4.9–5.01; Brown streak; Semimetallic to adamantine, greasy on fractures luster; optically uniaxial.
IMA symbol Caz, IMA status: approved, named in 1961.
A characteristic accessory mineral in alkalic and ultramafic complexes in association with carbonatites; typically found in residual soils and alluvium.
It is found associated with Forsterite, pyroxene, calcite, magnetite, phlogopite, niobian perovskite, apatite, rutile, anatase, baddeleyite, zirconolite.
The name refers to CALcium and ZIRconium in its composition.