Bustamite "eyes-chain" from Argentina.

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 830 °C (1,530 °F), 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. The type locality was originally taken as Tetela de Jonotla, Puebla, Mexico, and the mineral was named for General Anastasio Bustamante (1780–1853), three times President of Mexico. The material from Puebla, however, was later found to be a mixture of johannsenite and rhodonite, so the type locality is now the Franklin Mine, Franklin, Sussex County, New Jersey, US. Both bustamite and johansennite are found at Franklin.[3] Bustamite is moderately common there and occurs in a variety of assemblages, associated with rhodonite and tephroite, calcite and tephroite or glaucochroite and tephroite. Vesuvianite, wollastonite, garnet, diopside, willemite, johannsenite, margarosanite and clinohedrite also may be present.