Formula: (Na,K,Pb,Li)3(Ta,Nb,Al)11(O,OH)30
Origin of name: for K. Rankama, Finnish geochemist
Crystal system: orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell:
Colour: white to creamy white
Diaphaneity:
Luster:
Habit: massive, water-worn pebbles, felted
Hardness: 3 to 4
Specific gravity: 5.5
Cleavage: none
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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