Images
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
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).
Back to Minerals