Larnite is a calcium silicate mineral with the formula Ca2SiO4. It is the calcium member of the olivine group of minerals.
| Larnite | |
|---|---|
| General | |
| Category | Nesosilicates |
| Formula (repeating unit) | Ca2SiO4 |
| IMA symbol | Lrn[1] |
| Strunz classification | 9.AD.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/n |
| Unit cell | a = 5.5, b = 6.74 c = 9.29 [Å]; β = 94.59°; Z = 4 |
| Identification | |
| Color | White to gray |
| Crystal habit | Flattened anhedral grains; massive |
| Twinning | Common, polysynthetic parallel to {100} |
| Cleavage | Good on {100}, imperfect on {010} |
| Mohs scale hardness | 6 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.28–3.33 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.707 nβ = 1.715 nγ = 1.730 |
| Birefringence | δ = 0.023 |
| 2V angle | 74° calculated |
| Dispersion | r > v |
| References | [2] |
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–Ca2SiO4, sometimes represented by the idealized oxide formula 2CaO·SiO2 also noted C2S in the cement chemist notation (CCN). When used in the cement industry, the mineral is usually referred to as belite.
References
- Deer, William Alexander; Howie, R. A; Zussman, J (1986). "Larnite". Disilicates and ring silicates. pp. 248–249. ISBN 978-1-897799-89-5.