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Laurionite crystals in a vug from the Laurium district of Greece
Category Halide minerals
(repeating unit)
Strunz classification 3.DC.05
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pnma
Unit cell a = 7.111, b = 9.6987
c = 4.0203 [Å]; Z = 4
Color Colorless, white
Crystal habit Elongated tabular prismatic crystals
Cleavage Distinct on {101}
Tenacity Flexible
Mohs scale hardness 3 - 3.5
Luster Adamantine, pearly
Streak White
Diaphaneity Transparent
Specific gravity 6.241
Optical properties Biaxial (-)
Refractive index nα = 2.077 nβ = 2.116 nγ = 2.158
Birefringence δ = 0.081
2V angle Measured: 70°
Solubility Sleight in cold water
References [1][2][3][4]

Laurionite (PbCl(OH)) is a lead halide mineral. It forms colorless to white crystals in the orthorhombic crystal system and is dimorphous with paralaurionite, both members of the matlockite group.[1]

It was first described in 1887 for an occurrence in the Laurium District, Attica, Greece and named after the town Laurium.[1] It occurs as an oxidation product in lead ore deposits, and is also produced on lead-bearing slag by reaction with saline solutions. It occurs associated with paralaurionite, penfieldite, fiedlerite, phosgenite, cerussite and anglesite.[2]