augite

{{Infobox mineral | name = Augite | category = Inosilicate minerals (single chain) | group = Pyroxene group, clinopyroxene subgroup | image = Augite Rwanda.jpg | imagesize = 260px | alt = | caption = Augite – Muhavura volcano | formula = |IMAsymbol=Aug | molweight = | strunz = 9.DA.15 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | unit cell = a = 9.699, b = 8.844 c = 5.272 [Å] β = 106.97°; Z = 4 | color = Black, brown, greenish, violet-brown; in thin section, colorless to gray with zoning common | habit = Commonly as stubby prismatic crystals, also acicular, skeletal, dendritic | twinning = Simple or multiple on {100} and {001} | cleavage = {110} good with 87° between {110} and {10}; parting on {100} and {010} | fracture = uneven to conchoidal | tenacity = brittle | mohs = 5.5 to 6 | luster = Vitreous, resinous to dull | refractive = nα = 1.680–1.735, nβ = 1.684–1.741, nγ = 1.706–1.774 | opticalprop = Biaxial (+) | birefringence = δ = 0.026–0.039 | pleochroism = X = pale green, pale brown, green, greenish yellow; Y = pale brown, pale yellow-green, violet; Z = pale green, grayish green, violet | streak = Greenish-white | gravity = 3.19–3.56 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to opaque | other = | references = }}

Augite, also known as Augurite, is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.