Nealite Crystals
Nealite Crystals. From: Vrissaki Point slag locality, Vrissaki area, Attikí (Attica; Attika) Prefecture, Greece. Photo: Christian Rewitzer

A triclinic-pinacoidal mineral containing arsenic, chlorine, iron, lead, and oxygen.

Chemical Formula:  Pb4Fe(AsO4)2Cl4
Lustre: Adamantine, Vitreous, Sub-Vitreous
Transparency: Transparent
Colour: Yellow brown to orange brown
Streak: Pale yellow to pale orange
Hardness: 4 on Mohs scale
Tenacity: Very brittle
Cleavage: None Observed 

It was discovered in specimen from the ancient Greek mines of Lauryon, in Attica (Greece), which is consequently its type locality.

Nealite Crystals
Nealite Crystals. Locality: Lavrion Slag Localities, Lavreotiki, East Attica, Attiki Prefecture, Greece Photo: Joy Desor Mineralanalytik