Geographic Minerals



Clearcreekite is polymorphous with peterbaylissite. The chemical formula of clearcreekite is Hg1+3CO3(OH)∙2H2O. It is a monoclinic-prismatic pale greenish yellow mineral containing carbon, hydrogen, mercury, and oxygen.

Clearcreekite is an extremely rare mineral from the Clear Creek mercury mine, New Idria district, San Benito County, California. It was probably formed after the alteration of other mercury minerals such as cinnabar. The mineral is named after the locality where it was found.

General Information

  • Category: Carbonate mineral
  • Formula: Hg1+3CO3(OH)∙2H2O
  • Crystal system: Monoclinic
  • Crystal class: Prismatic (2/m) (same H-M symbol)


Clearcreekite is transparent with a pale greenish yellow color and streak, vitreous luster, good cleavage on {001} and it is brittle with an uneven fracture. Its density (calculated from the idealized formula) is 6.96 g/cm3. The mineral is monoclinic with the space group P2/c.

  • Color: pale greenish yellow
  • Crystal habit: tabular, subhedral
  • Cleavage: good on {001}
  • Fracture: uneven
  • Tenacity: brittle
  • Mohs scale hardness: probably 2
  • Luster: vitreous
  • Streak: pale greenish yellow
  • Density: 6.96 g/cm3 (calculated)

Geologic occurrence

Mercury deposits in California are located mainly along the San Andreas Fault. The deposits are related to the transition of the North American plate and the Pacific plate boundary from converging to transform. The crystals of clearcreekite were originally found on a silica-carbonate rock near specimens of cinnabar and edoylerite.


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