Bornemanite

Formula:  BaNa₄Ti₂NbSi₄O₁₇(F,OH) ^. Na₃PO₄

Origin of name:  For Irina D. Borneman-Starynkevich, Russian mineralogist, specialist in Khibiny and Lovozero minerals

Crystal system:  Orthorhombic

Crystal class:  mm2 or 2/m 2/m 2/m

Twinning:

Unit cell: a = 5.48 Å, b = 7.10 Å, c = 48.2 Å

Colour:  Pale yellow

Diaphaneity:  Transparent to translucent

Luster:  Pearly

Habit:  As platy aggregates

Hardness:  3.5 to 4

Specific gravity:  3.47 to 3.50

Cleavage:  1; {001} perfect

Tenacity: Brittle, fibers are flexible

Streak:

Synonyms/varieties:

Comments: Found in the natrolite zone of alkalic pegmatites in differentiated massifs.