Formula: Ba3(Nb,Ti)6(Si2O7)2O12
Origin of name: For Igor V. Bel'kov Russian mineralogist (1917-1989), who explored the Kola Peninsula, Russia
Crystal system: Hexagonal
Crystal class: -6m2
Twinning:
Unit cell: a = 8.966 Å, c = 7.799 Å
Colour: Brown
Diaphaneity: Transparent
Luster: Adamantine
Habit: Crystals to 1 mm, as thin rims on barian pyrochlore
Hardness: 6 to 7
Specific gravity: 4.16
Cleavage: None
Tenacity: Moderately brittle
Streak: White
Synonyms/varieties:
Comments: Found as secondary mineral, formed by alteration of barium-rich pyrochlore during dolomitisation of calcite carbonatites in pyroxenites.
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