Larnite

Larnite is a calcium silicate mineral with formula: Ca₂SiO₄. It is the calcium member of the olivine group of minerals.

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	[1]

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–Ca₂SiO₄, sometimes represented by the formula 2CaO·SiO₂. When used in the cement industry, the mineral is usually referred to as belite.

References

1. Larnite on Mindat.org

• Deer, William Alexander; Howie, R. A; Zussman, J (1986). "Larnite". Disilicates and ring silicates. pp. 248–249. ISBN 978-1-897799-89-5.