Arctite

Formula:  Na₅Ca₇Ba(PO₄)₆F₃

Origin of name:  After locality; in the Arctic, valley of the Vounnimi River, Khibina alkalic massif, Kola Peninsula, Russia

Crystal system:  Hexagonal

Crystal class:  -3 2/m

Twinning:

Unit cell: a = 7.094 Å, c = 41.320 Å

Colour:  Colourless

Diaphaneity: Transparent

Luster:  Vitreous, pearly on cleavages

Habit:

Hardness:  about 5

Specific gravity:  3.13

Cleavage:  1; {0001} perfect

Tenacity:

Streak: White

Synonyms/varieties:

Comments: Formed as a late-stage pneumatolytic mineral in pegmatite veinlets in a differentiated alkalic massif.