Kotoite

minerals

szaibelyite

suanite

warwickite

Formula: Mg3(BO3)2
Anhydrous borate
Specific gravity: 3.10
Hardness: 6½
Streak: White
Colour: Colourless; colourless in transmitted light
Solubility: Readily soluble in warm hydrochloric or sulphuric acid
Melting Point = ~ 1340oC
Environments

Metamorphic environments

Kotoite is an uncommon mineral typically formed in the contact zone of magnesium-rich skarn borate deposits (HOM).

Localities

At the Neichi mine, Japan, kotoite is associated with ludwigite, suanite, szaibélyite and warwickite (HOM).

At the type locality, the North orebody, Hol Kol Mine, Suan-gun, North Hwanghae Province, North Korea, kotoite is found in the contact metamorphic zone of a granitic intrusion into dolostone, associated with fosterite, norbergite, spinel, ludwigite, szaibélyite, fluoborite, clinohumite and dolomite (AM 24.406, HOM, Mindat).

Kotoite alters to szaibélyite under hydrothermal conditions (Dana).

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