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Bastite thin section

About Bastite
Name for pseudomorphs of serpentine group minerals after enstatite.
Bastite hand-specimen
Formula: (Mg, Fe, Ni, Mn, Al, Zn)3Si2O5(OH)4
System: Monoclinic
Color: Green, green-blue, white, brown, black
Lustre: Vitreous
Hardness: 3–4
Density: 2.5–2.6
Sillimanite #1 thin section (hFOV 2mm)
Bastite PPL properties
Relief: Low positive
Habit/Form: Can occur together with lizardite, which can form oriented pseudomorphs after orthopyroxene (bastite).
Color: Colorless to pale green
Pleochroism: Absent to weak
Cleavage: Perfect basal cleavage {001}
Bastite XPL properties
Isotropy/Anisotropy: Anisotropic
Interference color: Order I gray
Extinction angle: Parallel / 0° / straight to the length of crystals/fibers
Twins: Absent
Uniaxial/Biaxial: Biaxial (-)
Optic axial angle (2V): 2V 53 -125°
Bastite distinguishing features under the microscope
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  • Deer, W. A., Howie, R. A., & Zussman, J. (2013). An introduction to the rock-forming minerals (pp. 498). Mineralogical Society of Great Britain and Ireland, London.
  • mindat.org – The Mineral Database