Ilvaite, Quartz, Calcite, Hedenbergite Dimensions: 4.5 cm × 3.5 cm × 3.1 cm Locality: Dalnegorsk, Russia Description: Black Ilvaite crystals with colorless Quar — Photo: Raimond Spekking · CC BY-SA 4.0
Ilvaite
A black calcium-iron sorosilicate named for Elba (Ilva) — lustrous prismatic crystals prized by collectors.
Intro adapted from Wikipedia (CC BY-SA).
Ilvaite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaFe³⁺Fe²⁺₂O(Si₂O₇)(OH).
It crystallizes in the monoclinic crystal system (space group Pnam). It is a member of the Ilvaite structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 3.99–4.05; typically black or brown; Black, inclining to green or brown streak; Submetallic luster; optically biaxial.
IMA symbol Ilv, grandfathered status — known before the IMA’s founding, named in 1811.
Found in contact metasomatic rocks and iron deposits; in metamorphosed limestones and dolostones with other calc-silicate minerals.
It is found associated with Quartz, magnetite, hedenbergite, sphalerite, fluorite.
The name comes from the Latin name, Ilva, for the Island of Elba, on which it was first found.
Collections: Collector Favorites.