Larnite
Calcium orthosilicate — the calcium member of the olivine group, described in 1929 from Scawt Hill near Larne, Northern Ireland.
Intro adapted from Wikipedia (CC BY-SA).
Larnite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂(SiO₄).
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: Mohs hardness 6; specific gravity 3.28–3.33; Vitreous luster; refractive index 1.717; optically biaxial.
IMA symbol Lrn, grandfathered status — known before the IMA’s founding, named in 1929.
Found in contact metamorphic terranes involving sedimentary carbonate rocks.
It is found associated with Spurrite, melilite, gehlenite, merwinite, perovskite, wollastonite (Scawt Hill, Ireland); rankinite, kilchoanite, scawtite, hydrogrossular (Tokatoka district.
The name refers to Larne, Ireland, in the vicinity of which the mineral was initially observed.