Heliophyllite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameHeliophyllite
Chemical FormulaPb6As2O7Cl4
Mohs Hardness2.5
Crystal Systemorthorhombic
Lusteradamantine
Streak Colorpale yellow
Cleavagegood on {001}
Fractureuneven
Specific Gravity6.8
Colorsyellow, orange-yellow, brownish-yellow
Transparencytranslucent
Type LocalityThorikos Bay slag locality, Thorikos area, Lavrion District slag localities, Lavrion (Laurion; Laurium) District, Attikí (Attica; Attika) Prefecture, Greece
Mineral GroupArsenate-Halide
Usescollector, scientific
Associated Mineralscerussite, anglesite, mimetite, iron oxides
Rarityrare
Description
This image displays small, yellowish-orange, botryoidal (spherical) aggregates of heliophyllite nestled within a dark, rough matrix, likely a cavity in ancient mining slag.
Geological Context
Heliophyllite is a rare secondary mineral that forms in the oxidized zones of lead-arsenic ore deposits, frequently found in ancient mining slags where primary minerals have undergone weathering and alteration.
