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

Larnite
General
CategoryNesosilicates
Formula
(repeating unit)
Ca2SiO4
IMA symbolLrn[1]
Strunz classification9.AD.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/n
Unit cella = 5.5, b = 6.74
c = 9.29 [Å]; β = 94.59°; Z = 4
Identification
ColorWhite to gray
Crystal habitFlattened anhedral grains; massive
TwinningCommon, polysynthetic parallel to {100}
CleavageGood on {100}, imperfect on {010}
Mohs scale hardness6
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity3.28–3.33
Optical propertiesBiaxial (+)
Refractive indexnα = 1.707 nβ = 1.715 nγ = 1.730
Birefringenceδ = 0.023
2V angle74° calculated
Dispersionr > 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

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  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Larnite on Mindat.org