anthophyllite

{{Infobox mineral | name = Anthophyllite | category = InosilicatesAmphibole | image = Anthophyllite Suède Fond.jpg | imagesize = 260px | alt = | caption = | formula = ☐Mg2Mg5Si8O22(OH)2 |IMAsymbol=Ath | strunz = 9.DE.05 | system = Orthorhombic | class = Dipyramidal (mmm)H-M symbol: (2/m 2/m 2/m) | symmetry = Pnma | unit cell = a = 18.5, b = 17.9c = 5.28 [Å]; Z = 4 | color = Gray to green, brown, and beige | habit = Rarely as distinct crystals. Commonly lamellar or fibrous. | twinning = | cleavage = Perfect on {210}, imperfect on {010}, {100} | fracture = | tenacity = Brittle; elastic when fibrous | mohs = 5.5 – 6 | luster = Vitreous, pearly on cleavage | refractive = nα=1.598 – 1.674, nβ=1.605 – 1.685, nγ=1.615 – 1.697; indices increase with Fe content | opticalprop = Biaxial (+) | 2V = 57° - 90° | birefringence = δ = 0.017 – 0.023 | pleochroism = | streak = White to gray | gravity = 2.85 – 3.2 | melt = | fusibility = | diagnostic = Characterized by clove brown color, but unless in crystals, difficult to distinguish from other amphiboles without optical and/or X-ray tests | solubility = | diaphaneity = Transparent to translucent | other = | references = }}

Anthophyllite is an orthorhombic amphibole mineral: ☐Mg2Mg5Si8O22(OH)2 (☐ is for a vacancy, a point defect in the crystal structure), magnesium iron inosilicate hydroxide. Anthophyllite is polymorphic with cummingtonite. Some forms of anthophyllite are lamellar or fibrous and are classed as asbestos. The name is derived from the Latin word anthophyllum, meaning clove, an allusion to the most common color of the mineral. The Anthophyllite crystal is characterized by its perfect cleavage along directions 126 degrees and 54 degrees.