• Chemistry: Pb9As4S15, Lead Arsenic Sulfide
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Uses: Mineral specimens and as a very minor ore of lead.
  • Specimens

Gratonite is a rare lead sulfide mineral. It forms nice crystals that can be arranged into rosette-like clusters with projecting rhombohedral terminations. Clusters can be attractive and good specimens command large prices, mostly because of the rarity of the mineral. Gratonite is a sulfosalt, a segment of sulfides where the arsenic acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs.

Also, Gratonite is the most common mineral whose symmetry is in the Trigonal Pyramidal Class


  • Color is a dark lead gray.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Trigonal; 3
  • Crystal Habits include rhombohedral as well as hexagonal prismatic crystals capped by three rhombohedral faces. Clusters can be found in rosette-like aggregates, also massive.
  • Cleavage: None.
  • Fracture: Subconchoidal.
  • Hardness is 2.5
  • Specific Gravity is 6.2 (heavier than average for metallic minerals)
  • Streak is gray.
  • Notable Occurrences are limited to the Excelsior Mine, Cerro de Pasco, Peru.
  • Best Field Indicators are crystal habit, locality, color and density.
GRATONITE specimens:
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GRATONITE specimen grt-1
$ 60.00
Dims:0.7x0.3x0.2" (1.8x0.8x0.5 cm)
Wt: 0.1oz. (3g)
Excelsior Mine, Cerro de Pasco, Peru
The surface of this micro-sized specimen is covered with tiny, lead-gray crystals of gratonite. These crystals are undamaged, and, with a loupe, one can observe the hexagonal form of these crystals. One of the larger crystals seems to be in the form of a scalenohedron. Greater magnification is needed for verication of this. Gratonite is named for the American geologist, Louis Graton.
no photo
grt-1 ($ 60.00)
Excelsior Mine, Cerro de Pasco, Peru


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