Geographic Minerals



Georgerobinsonite, named for George Willard Robinson, is a lead chromate mineral with formula Pb4(CrO4)2(OH)2FCl. The type specimen for georgerobinsonite was found in the Mammoth-St. Anthony Mine in Tiger, Arizona.

Georgerobinsonite is named for George Willard Robinson, A. E. Seaman Mineral Museum curator since 1996 and mineralogy professor at Michigan Technological University.

General Information

  • Category: Mineral
  • Formula: Pb4(CrO4)2(OH)2FCl
  • Crystal system: Orthorombic
  • Crystal class: Dipyramidal (mmm)

Fig: Georgerobinsonite


Georgerobinsonite is a soft, brittle mineral that forms crystals less than 0.1 mm (0.0039 in) across. The mineral possesses a pale-orange streak and an adamantine luster. It is most strongly associated with cerussite and diaboleite.

  • Color: Orange-red
  • Fracture: Uneven
  • Mohs scale hardness: 2.5-3
  • Luster: Adamantine luster
  • Streak: Pale orange
  • Density: 6.23 g/cm3 (calculated)


Georgerobinsonite is orange-red, transparent and has a pale orange streak and an adamantine luster, and it does not fluoresce under ultraviolet light. It exhibits very small, transparent crystals with a bright orange-red color. It was obtained from the Mammoth-St. Anthony Mine in Arizona in the 1940s and identified in 2009.

The sample was collected by Dan Mayers in 1943 or 1944. At this time, the mine was operating at a level where a number of exotic minerals have been discovered. The exact location of its origin is unknown, but it is likely from the Collins vein at the 500 level.


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