Larnite

Ca₂SiO₄IMA symbolLrn^[1]Strunz classification9.AD.05Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP2₁/nUnit cella = 5.5, b = 6.74
c = 9.29 [Å]; β = 94.59°; Z = 4IdentificationColorWhite to grayCrystal habitFlattened anhedral grains; massiveTwinningCommon, polysynthetic parallel to {100}CleavageGood on {100}, imperfect on {010}Mohs scale hardness6LusterVitreousStreakWhiteDiaphaneityTransparent to translucentSpecific gravity3.28–3.33Optical propertiesBiaxial (+)Refractive indexn_α = 1.707 n_β = 1.715 n_γ = 1.730Birefringenceδ = 0.0232V angle74° calculatedDispersionr > vReferences^[2]

Larnite is a calcium silicate mineral with the formula Ca₂SiO₄. 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–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.