Megawite

megawite

perovskite

lakargiite

larnite

Images

Formula: CaSnO3
Oxide, perovskite subgroup, stoichiometric perovskites group, perovskite supergroup, tin-bearing mineral, forms series with perovskite and lakargiite
Crystal System: Orthorhombic
Specific gravity: 5.06 calculated
Streak: White
Colour: Pale yellowish brown, pale yellow to colourless
Environments

Metamorphic environments

Megawite was approved in 2010 but to date (June 2025) it has been reported only from the Lakargi Mountain.

Localities

The type locality is Xenolith no. 3, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District, Kabardino-Balkaria, Russia.

At Xenolith no. 1, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District, Kabardino-Balkaria, Russia, crystals of zirconium-bearing megawite were found in the spurrite zones of the skarned xenolith in ignimbrites. Xenolith no. 1 is the type locality for thirteen minerals, including lakargiite, chegemite, kumtyubeite, bitikleite and elbrusite.
Zirconium-bearing megawite occurs with spurrite, hydroxylellestadite, rondorfite, wadalite, minerals of the reinhardbraunsite - kumtyubeite series, calcite and rarely periclase. Accessory and rare minerals are represented by the perovskite subgroup minerals lakargiite and perovskite, the garnet supergroup minerals kerimasite and elbrusite, and by srebrodolskite, and a mineral with the formula Ca3TiFe2O8. Spurrite crystals are embedded in the mass of secondary minerals among which hydrocalumite, ettringite group minerals, hydrogrossular, afwillite and other hydrosilicates are widespread. Brucite develops after periclase.
Zirconium-bearing megawite crystals from the holotype sample do not exceed 15 microns in size and usually occur as inclusions in spurrite. Numerous lakargiite crystals occur between spurrite grains in wadalite - calcite - hydrocalumite - ettringite aggregates. Homogeneous megawite and lakargiite crystals are commonly found in the same spurrite crystal (MM 75.5.2563-2572).

The type locality for megawite is Xenolith no. 3, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District, Kabardino-Balkaria, Russia, which is also the type locality for toturite, pavlovskyite and rusinovite. Megawite was found here forming rims on micron-sized lakargiite crystals in larnite-cuspidine zones in skarns which contain abundant hydrogarnet and hydrosilicates. Megawite and garnets (toturite and tin-bearing schorlomite) form rims on lakargiite pseudomorphs after zircon. Megawite from xenolith no. 3 contains considerable CaZrO3 and CaTiO3, and also U, Nb and Fe impurities (MM 75.5.2563-2572).
Megawite from Xenolith no. 3 - Image

At Xenolith no. 7, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District, Kabardino-Balkaria, Russia, tin-rich lakargiite was found, as well as the type specimens of vorlanite and irinarassite. Crystals of tin-rich lakargiite overgrow porous, fine-grained aggregates of almost pure lakargiite, which occur with relict larnite, rondorfite, wadalite, magnesioferrite, arsenic-bearing hydroxylellestadite and srebrodolskite. Rarely, megawite occurs as rims up to 5 microns thick on tin-rich lakargiite crystals in the highly altered parts of the chegemite-bearing skarns which contain hydrogarnet and ettringite. The megawite composition approaches the boundary with lakargiite. A phase close to burtite, which overgrows the lakargiite aggregates, is also found in this association.
Megawite crystals are transparent and pale yellow or colourless with a vitreous lustre and a white streak (MM 75.5.2563-2572).

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