Pargasite
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Pargasite or pargasitic hornblende is a complex inosilicate mineral of the amphibole group with formula NaCa₂O₂₂(OH)₂.
It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality. Wikipedia
Optical properties: Biaxial (−)
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Stout prismatic to tabular
Crystal system: Monoclinic
Formula (repeating unit): NaCa2(Mg4Al)(Si6Al2)O22(OH)2
Mohs scale hardness: 5–6
Refractive index: nα = 1.630 nβ = 1.640 nγ = 1.650
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