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|Name:||After the type locality, Scawt Hill, Larne, Co. Antrim, Northern Ireland, UK.|
Olivine Group. The high-temperature, monoclinic polymorph of Calcio-Olivine.
Larnite crystallizes at high temperatures. It occurs in limestones or chalk zones in contact with molten basaltic rocks. Larnite is stable in the range of 520° to 670° C; otherwise, it is only metastable at lower temperatures and inverts to its low-temperature polymorph, Calcio-Olivine, when shocked.
An important phase (Belite, β-C2S) in cement clinker.
Five polymorphs of Ca2SiO4 are known; some are stabilised by impurities.
Classification of Larnite
|IMA status:||Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"|
|Strunz 8th edition ID:||8/A.07-30|
|Nickel-Strunz 10th (pending) edition ID:||9.AD.05|
9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in  and/or greater coordination
|Dana 8th edition ID:||184.108.40.206|
51 : NESOSILICATES Insular SiO4 Groups Only
5 : Insular SiO4 Groups Only with cations in > coordination
|Hey's CIM Ref.:||14.5.6|
14 : Silicates not Containing Aluminum
5 : Silicates of Ca
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Type Occurrence of Larnite
|Type Locality:||Scawt Hill, Larne, Co. Antrim, Northern Ireland, UK|
|Year of Discovery:||1929|
|Associated Minerals at type locality:|
Occurrences of Larnite
|Geological Setting:||Metamorphosed sedimentary carbonate formations in contact with basaltic rocks.|
Physical Properties of Larnite
Crystallography of Larnite
|Cell Parameters:||a = 5.5Å, b = 6.74Å, c = 9.29Å|
β = 94.59°
|Ratio:||a:b:c = 0.816 : 1 : 1.378|
|Unit Cell Volume:||V 343.28 Å³ (Calculated from Unit Cell)|
Optical Data of Larnite
|RI values:||nα = 1.707 nβ = 1.715 nγ = 1.730|
|Maximum Birefringence:||δ = 0.023|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Dispersion:||r > v|
Chemical Properties of Larnite
|Essential elements:||Ca, O, Si|
|All elements listed in formula:||Ca, O, Si|
Relationship of Larnite to other Species
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Larnite
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Larnite
Tilley, C.E. (1929) On larnite (calcium orthosilicate, a new mineral) and its associated minerals from the limestone contact-zone of Scawt Hill, Co. Antrim. Mineralogical Magazine, 22, 77-86.
American Mineralogist (1929): 14: 338.
American Mineralogist (1966): 51: 1766.
Jost, K.H., B. Ziemer, and R. Seydel (1977) Redetermination of the structure of dicalcium silicate. Acta Crystallographica: B33: 1696-1700.
Deer, W.A., R.A. Howie, and J. Zussman (1986) Rock-forming minerals, (2nd edition), v. 1B, disilicates and ring silicates, 248-255.
Martínez-Frías, J., Benito, R., Wilson, G., Delgado, A., Boyd, T., and Marti, K. (2004): Analysis and chemical composition of larnite-rich ultrarefractory materials. Journal of Materials Processing Technology 147, 204–210.
Internet Links for Larnite
Localities for Larnite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.