Crestmore - Riverside County California, USA — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Monticellite
The magnesium end of the monticellite-kirschsteinite olivine-group pair — calcium-magnesium silicate of skarns.
Intro adapted from Wikipedia (CC BY-SA).
Monticellite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaMg(SiO₄).
It crystallizes in the orthorhombic crystal system (space group Pbnm). It is a member of the Olivine structural group.
Key properties: Mohs hardness 5.5; specific gravity 3.03–3.27; typically colorless or gray or green; White streak; Vitreous, slightly resinous when massive luster; refractive index 1.654; optically biaxial.
IMA symbol Mtc, grandfathered status — known before the IMA’s founding, named in 1831.
developed during metamorphism of siliceous dolostones; in contact metamorphic deposits between limestones and olivine gabbros; in skarns at granite-dolomitic limestone contacts; rarely in kimberlites.
It is found associated with Gehlenite, spinel, calcite, merwinite, º akermanite, vesuvianite, apatite, cuspidine.
The name refers to the Italian mineralogist Teodoro Monticelli (1759–1845).
Collections: Collector Favorites, Rare & Remarkable.