1) Magnesium mineral 
Cummingtonite is a metamorphic amphibole with the chemical composition ☐Mg2Mg5Si8O22(OH)2, magnesium iron silicate hydroxide. Monoclinic cummingtonite is compositionally similar and polymorphic with orthorhombic anthophyllite, which is a much more common form of magnesium-rich amphibole, the latter being metastable. Cummingtonite shares few comp...
an amphibole mineral, an iron and magnesium silicate that occurs in metamorphic rocks. For chemical formula and detailed physical properties, see ... [1 related articles]
an amphibole mineral, magnesium-iron silicate, similar in composition to anthophyllite but richer in iron.