Larnite
| Larnite | |
|---|---|
| General | |
| Category | Nesosilicates |
|
Formula (repeating unit) |
Ca2SiO4 |
| 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 | |
Larnite is a calcium silicate mineral with formula: Ca2SiO4.
It was first described from an occurrence at Scawt Hill, Larne, Northern Ireland in 1929 by Cecil Edgar Tilley and named for the location. 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.
Dicalcium silicate is chemically, β–Ca2SiO4, sometimes represented by the formula 2CaO·SiO2. When used in the cement industry, the mineral is usually referred to as belite.
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