Idocrase
1 in the gallery
Idocrase is a calcium-iron-aluminum inosilicate mineral that forms in metamorphic rocks and contact aureoles. Crystals are typically prismatic to blocky, often showing a vitreous to pearly luster and a green to olive-brown color. The mineral commonly crystallizes in granular to compact aggregate habits, and may occur as platy or faceted crystals in well-formed specimens. Notable localities include classic deposits in the United States and Canada, with additional finds in Mali contributing to its rarity in hand specimens.
- Formula
- Ca19Fe3+Al4(Al6Mg2)(◻4)◻[Si2O7]4[(SiO4)10]O(OH)9
- Rarity
- Common
- Stability
- Stable
- Collector interest
- Moderate Interest
- Classification notes
- Silicate; Epidote group (sorosilicate)
Where Idocrase is found
Top localities
- Jeffrey Mine1 specimen
About Idocrase
Collectors prize Idocrase for its rich, sometimes lustrous crystals and its distinctive green hues that contrast with more common metamorphic minerals. Specimens from well-known localities often display good transparency, pleasing color zoning, and sharp termination faces, making them attractive for display and study. Its geological occurrence highlights the interplay of metamorphism and mineral chemistry, appealing to collectors who value both aesthetics and the scientific background of mineral formation.