aegirine

{{Infobox mineral | name = Aegirine | category = Silicate mineral, pyroxene | image = Aegirine - Mt Malosa, Zomba, Malawi (alt).jpg | caption = Aegirine (dark) with minor feldspar (light) from Malawi | formula = |IMAsymbol=Aeg | molweight = 231.00 g/mol | strunz = 9.DA.25 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | unit cell = a = 9.658, b = 8.795 c = 5.294 [Å], β = 107.42°; Z = 4 | color = Dark Green, Greenish Black | habit = Prismatic crystals may be in sprays of acicular crystals, fibrous, in radial concretions | twinning = Simple and lamellar twinning common on {100} | cleavage = Good on {110}, (110) ^ (10) ≈87°; parting on {100} | fracture = Uneven | tenacity = Brittle | mohs = 6 | luster = Vitreous to slightly resinous | polish = | refractive = nα = 1.720 – 1.778 nβ = 1.740 – 1.819 nγ = 1.757 – 1.839 | opticalprop = Biaxial (−) | birefringence = δ = 0.037 – 0.061 | dispersion = moderate to strong r > v | pleochroism = X = emerald green, deep green; Y = grass-green, deep green, yellow; Z = brownish green, green, yellowish brown, yellow | fluorescence= | absorption = | 2V = Measured: 60° to 90°, Calculated: 68° to 84° | streak = Yellowish-grey | gravity = 3.50–3.60 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent to opaque | other = | references = }}

Aegirine is a mineral. It is a member of the clinopyroxene group of inosilicate minerals. Acmite is a fibrous green-colored variety of aegirine, with the name also used as a synonym. It was first described in 1821, in Kongsberg, Norway.