Larnite

Short description: Calcium silicate mineral

Larnite

General
Category| Nesosilicates
Formula
(repeating unit)| Ca
2SiO

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
|re|er}}| 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| [1]

Larnite is a calcium silicate mineral with the formula Ca
2SiO
4. 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.[1] 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.[1]

Dicalcium silicate is chemically β–Ca
2SiO
4, sometimes represented by the idealized oxide formula 2CaO·SiO
2 also noted C
2S in the cement chemist notation (CCN). When used in the cement industry, the mineral is usually referred to as belite.

## References

1. ↑ 1.0 1.1 1.2 Larnite on Mindat.org
2. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.

* Deer, William Alexander; Howie, R. A; Zussman, J (1986). "Larnite". Disilicates and ring silicates. pp. 248–249. ISBN 978-1-897799-89-5. https://books.google.com/books?id=XT3cj5U2WEIC&pg=PA248.

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