Sulphohalite is a rare sodium sulfate evaporite mineral that only occurs in three locations in the world; Namibia, Russia and California, USA. The most well known and best location for gemmy crystals is Searles Lake, San Bernardino County, California, USA. At Searles Lake Sulphohalite is associated with Halite and Hanksite.

Sulphohalite can be found at the Otjiwalundo salt pan, about 400 km west-northwest of Otavi, Namibia; from volcanoes on the Kamchatka Peninsula, Russia; and Searles Lake, San Bernardino County, California, USA.

Chemical Formula: Na6(SO4)2FCl
Sodium Sulfur Fluorine Sulfate
Molecular Weight: 384.52 gm
Sodium 35.87 % Na 48.36 % Na2O
Sulfur 16.68 % S 41.64 % SO3
Chlorine 9.22 % Cl 9.22 % Cl
—   % Cl -2.08 % -O=Cl2
Oxygen 33.29 % O
Fluorine 4.94 % F 4.94 % F
—   % F -2.08 % -O=F2
  100.00 % 100.00 % = TOTAL OXIDE


Crystallography: Isometric – Hexoctahedral
Crystal Habit: Octahedral, dodecahedral, cubic, or in combinations thereof, to 3 cm.
Twinning: None


Cleavage: {???} Perfect
Fracture: Conchoidal to Sub-Conchoidal
Tenacity: Brittle
Moh’s Hardness: 3.5
Density: 2.489 – 2.50 (g/cm3)
Luminescence: Fluorescent and Phosphorescent; bright white to creamy white under LW UV
Radioactivity: Not Radioactive  
Other: Slowly soluble in cold water.


Color: Colorless, Gray, Greenish Yellow; Colorless in transmitted light
Transparency: Transparent
Luster: Vitreous to Greasy (weak)
Refractive Index: 1.455 Isotropic
Birefringence: 0.0140
Dispersion: Very high
Pleochroism: Very Strong
Anisotrophism: Very Strong; Color in reflected light: