Carmichaelite

carmichaelite

pyrope

rutile

srilankite

Images

Formula: (Ti,Cr,Fe)(O,OH)₂
Oxide, titanium- and chromium- bearing mineral
Crystal System: Monoclinic
Specific gravity: 4.13 calculated
Hardness: 6
Colour: Cinnamon-brown
Environments

Igneous environments

Carmichaelite is thought to form in saline marine deposits by reaction of pre-existing saline minerals with fluids high in potash (potassium carbonate). Associated minerals include kieserite, sylvite, halite, polyhalite and bischofite (HOM).

Localities

At the type locality, Garnet Ridge, Dinnehotso, Apache County, Arizona, USA, occurs as platy, cinnamon-brown inclusions in mantle-derived pyrope crystals, which also contain inclusions of rutile, srilankite, ilmenite, minerals of the crichtonite group, spinel and olivine. Carmichaelite is commonly in contact with rutile and occasionally with srilankite. It is inferred to have co-precipitated with its pyrope host and other titanates in the presence of a fluid or melt phase at temperatures of 650 to 750°C and pressures of 20 to 25 kbar. It contains the highest OH content reported for titanates of mantle origin. It is probably stabilised by high pressure and the high concentration of chromium (AM 85.792-800).

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