Warwickite

warwickite

sinhalite

szaibelyite

kotoite

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Formula: (Mg,Ti,Fe,Cr,Al)2O(BO3)
Anhydrous borate, warwickite group
Crystal System: Orthorhombic
Specific gravity: 3.34 to 3.36 measured, 3.40 calculated
Hardness: 5½ to 6
Streak: Bluish black
Colour: Dark brown, grey to black, coppery tinge on cleavage at times, reddish brown in transmitted light
Solubility: Decomposed in sulphuric acid
Environments

Metamorphic environments

Warwickite is a rare accessory mineral in boron-metasomatised limestone and associated skarn. Associated minerals include chondrodite, szaibélyite, sinhalite, spinel, diopside, titanite, dravite, apatite, fluorite, scapolite, graphite, magnetite, ilmenite, pyrite and pyrrhotite (HOM).

Localities

At the type locality, Warwick, Orange county, New York, USA, warwickite was initially found as small, rough crystals in the metamorphosed, crystalline marble known as Franklin marble, associated with spinel, magnetite, ilmenite, graphite, diopside and chondrodite (Mindat).

At the Balmat-Edwards Zinc Mining District, St. Lawrence County, New York, USA, warwickite has been discovered in the Edwards and Balmat #3 mines. The samples from the two mines are similar in chemistry and atomic arrangement but differ chemically from previously described samples; they are among the most iron-poor samples described up to March 2020. The warwickite in the Edwards Mine sample occurs as 1 to 2 mm-diameter green crystals associated with pink spinel, forsterite, phlogopite and pyrite in an impure dolomitic marble, whereas warwickite in the specimens from the Balmat #3 mine, approximately 10 km distant, occurs as brown to amber coloured, slender, elongate, millimeter-size crystals in a calcitic marble in association with pink spinel, phlogopite, anhydrite, pyrite and galena (CM 58.2.183-190).

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