Larnite

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. Larnite is NOT a member of the olivine group.

History

Activities related to discovery and approval of the group members

Structural context

Larnite
Crystal System monoclinicSpace Group P21/c
a5.5019—5.515 (5.507)
b6.7505—6.764 (6.7559)
c9.3051—9.3408 (9.3197)
alpha90
beta94.144—94.597 (94.4608)
gamma90
volume344.849—346.718 (345.6831)

Based on 8 measurements

Chemical context

Stoichiometric formulas

Larnite
mindat.org
  • March 13, 2023Ca2SiO4
IMA
  • March 13, 2023Ca2(SiO4)
mineralogy.rocks
  • Aug. 30, 2022ß-Ca2SiO4

Elements recorded on EPMA

7
Ca
7
O
7
Si

Physical properties

ColorColor entities, recognized using a custom trained NER model
    • gray
    • colorless
    Color noteOriginal color note from the source
    White, gray, colorless in thin section
    Lustre
    Vitreous
    Transparency
    Transparent
    Translucent
    Hardness
    6
    Measured density
    3.28—3.33
    Calculated density
    3.326