Formula: PbCr2(CO3)2(OH)4·H2O
Origin of name: for amateur mineralogist William Frederick Petterd (1849-1910).
Crystal system: Orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 9.079, b = 16.321, c = 5.786
Colour: Pale to deep lilac, pinkish violet, pale gray
Diaphaneity: Translucent
Luster: Pearly to earthy
Habit: Encrustations, platy, roughly rectangular, with frayed and corroded terminations in the direction of [001]
Hardness: 2 (by analogy with dundasite)
Specific gravity: 3.947 (calculated)
Cleavage: 2; {100} fair, {010} possible
Tenacity:
Streak: Pale violet
Synonyms/varieties:
Comments:
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