Augite

Augite
Augite – Muhavura volcano
General
CategoryInosilicates
Formula
(repeating unit)
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6
IMA symbolAug[1]
Strunz classification9.DA.15
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 9.699, b = 8.844
c = 5.272 [Å]
β = 106.97°; Z = 4
Identification
ColorBlack, brown, greenish, violet-brown; in thin section, colorless to gray with zoning common
Crystal habitCommonly as stubby prismatic crystals, also acicular, skeletal, dendritic
TwinningSimple or multiple on {100} and {001}
Cleavage{110} good with 87° between {110} and {110}; parting on {100} and {010}
Fractureuneven to conchoidal
Tenacitybrittle
Mohs scale hardness5.5 to 6
LusterVitreous, resinous to dull
StreakGreenish-white
DiaphaneityTransparent to opaque
Specific gravity3.19–3.56
Optical propertiesBiaxial (+)
Refractive indexnα = 1.680–1.735, nβ = 1.684–1.741, nγ = 1.706–1.774
Birefringenceδ = 0.026–0.039
PleochroismX = pale green, pale brown, green, greenish yellow; Y = pale brown, pale yellow-green, violet; Z = pale green, grayish green, violet
References[2][3][4]

Augite, also known as Augurite, is a common rock-forming pyroxene mineral with formula (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ Augite on Mindat.org
  4. ^ Webmineral data for Augite