Tschermakite
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The endmember hornblende tschermakite is a calcium rich monoclinic amphibole mineral. It is frequently synthesized along with its ternary solid solution series members tremolite and cummingtonite so ... Wikipedia
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: As prismatic crystals or as reaction rims on other minerals
Crystal system: Monoclinic
Formula (repeating unit): ☐Ca2(Mg3Al2)(Si6Al2)O22(OH)2
Optical properties: Biaxial (−)
Unit cell: a = 9.762(6) Å; b = 17.994(12) Å; c = 5.325(6) Å; β = 105.10(8)°; Z = 2