| Larnite | |
| Category: | Nesosilicates |
| Imasymbol: | Lrn[1] |
| Strunz: | 9.AD.05 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | P21/n |
| Unit Cell: | a = 5.5, b = 6.74 c = 9.29 [Å]; β = 94.59°; Z = 4 |
| Color: | White to gray |
| Habit: | Flattened anhedral grains; massive |
| Twinning: | Common, polysynthetic parallel to |
| Cleavage: | Good on, imperfect on |
| Mohs: | 6 |
| Luster: | Vitreous |
| Streak: | White |
| Diaphaneity: | Transparent to translucent |
| Gravity: | 3.28–3.33 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.707 nβ = 1.715 nγ = 1.730 |
| Birefringence: | δ = 0.023 |
| 2V: | 74° calculated |
| Dispersion: | r > v |
| References: | [2] |
Larnite is a calcium silicate mineral with the formula . It is the calcium member of the olivine group of minerals.
It was first described from an occurrence at Scawt Hill, Larne, Northern Ireland in 1929 by Cecil Edgar Tilley and named for the location.[2] At the type locality it occurs with wollastonite, spurrite, perovskite, merwinite, melilite and gehlenite. It occurs in contact metamorphosed limestones and chalks adjacent to basaltic intrusives.[2]
Dicalcium silicate is chemically β–, sometimes represented by the idealized oxide formula also noted in the cement chemist notation (CCN). When used in the cement industry, the mineral is usually referred to as belite.