bustamite

{{Infobox mineral | name = Bustamite | category = Inosilicate | image = Bustamite.jpg | imagesize = | caption = Bustamite (pink) with galena (grey) from Broken Hill, New South Wales, Australia. Specimen size 3.7 cm. | formula = CaMn2+Si2O6 | IMAsymbol=Bst | molweight = | strunz = 9.DG.05 (10 ed) 8/F.18.40 (8 ed) | dana = 65.2.1.2 | system = Triclinic | class = Pinacoidal (same H-M symbol) | symmetry = I | color = Light pink to brownish red Pink color fades on exposure to sunlight | habit = Usually tabular or equant to prismatic; commonly massive, often compact and fibrous | twinning = Rare. Simple twins with (110) as the composition plane | cleavage = {100} perfect; {110} and {10} good; {010} poor | fracture = | tenacity = | mohs = 5.5 to 6.5 | luster = Vitreous | refractive = nα = 1.640 – 1.695, nβ = 1.651 – 1.708, nγ = 1.653 – 1.710 | opticalprop = Biaxial (−), 2V=34° to 60° | birefringence = δ = 0.013 – 0.015 Dispersion r Specimens from the Franklin Mine are fluorescent red in longwave ultraviolet light. Not radioactive | references = }} Bustamite is a calcium manganese inosilicate (chain silicate) and a member of the wollastonite group. Magnesium, zinc and iron are common impurities substituting for manganese. Bustamite is the high-temperature polymorph of CaMnSi2O6 and johannsenite is the low temperature polymorph. The inversion takes place at , but may be very slow.Bustamite could be confused with light-colored rhodonite or pyroxmangite, but both these minerals are biaxial (+) whereas bustamite is biaxial (−).

==Cell parameters== There is considerable variety in the literature about the size and type of the unit cell, the formula to be used, and the value of Z, the number of formula units per unit cell.