Formula: (Na,Ca,K)(Nb,Ti)Si2O6(O,OH).2H2O
Origin of name: for K. Nenadkevich, Russian mineralogist
Crystal system: orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 7.408 Å, b = 14.20 Ö, c = 7.148 Å
Colour: dark brown, brown to rose, yellow to tan
Diaphaneity:
Luster: dull
Habit: foliated masses to 4 cm across
Hardness: about 5
Specific gravity: 2.83
Cleavage: 1; {001} poor
Tenacity: uneven
Streak: pale rose
Synonyms/varieties:
Comments:
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