larnite

(mineralogy) β-Ca₂SiO₄ A gray mineral that is a metastable monoclinic phase of calcium orthosilicate, stable from 520 to 670°C. Also known as belite.

The alpha polymorph of calcium silicate (Ca₂SiO₄). Larnite is a mineral which crystallizes at high temperature. Its occurrences are practically confined to limestone or chalk zones in contact with semimolten basalts. At room temperature, larnite is metastable and inverts to its low-temperature polymorph calcio-olivine through shock. This leads to “fall,” or disintegration of slags with time, and presents problems in the cement industry. The mineral is very rare, known from its type locality at Scawt Hill, County Antrim, Ireland, and from Crestmore, near Riverside, California. See also Silicate minerals.

A mineral which is a major constituent of portland cement; beta dicalcium silicate.