Formula: (Sr,Ca)(Li,Na)2Al4(PO4)4(OH)4
Origin of name: after locality Palermo pegmatite, N. Groton, New Hampshire, USA
Crystal system: orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 11.56 Å, b = 15.85 Å, c = 7.315 Å
Colour: colourless to white
Diaphaneity:
Luster: vitreous to subadamantine
Habit: crystals long prismatic, striated vertically
Hardness: 5.5
Specific gravity: 3.22
Cleavage: 2; {100} perfect, {001} fair
Tenacity: subconchoidal to fibrous, brittle
Streak: white
Synonyms/varieties:
Comments: fluoresces white in direct X-ray beam
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