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A brownish-white ore containing Mercurous chloride. The name 'Calomel' is also used to refer to pure mercurous chloride. It has been used as a Fungicide, Insecticide, and topical anesthetic. One Peruvian cabinet decorated with mopa-mopa, was found to contain calomel as a white pigment (Newman 2015).

Synonyms and Related Terms

mercury chloride; mercurous chloride; mercury subchloride; mercury monochloride; mercury protochloride; precipité blanc; Calogreen; Cyclosan, M-C Turf fungicide; calomel (Fr.); calomelano (Esp., Port.); Calomel (Deut.)

Chemical structure



  • Toxic by ingestion, inhalation and skin absorption.
  • echemi: SDS

Physical and Chemical Properties

  • Tabular crystals or mass.
  • Cleavage = good in one direction.
  • Luster = adamantine
Composition Hg2Cl2
CAS 10112-91-1
Mohs Hardness 1.5
Density 7.15 g/ml
Molecular Weight mol. wt. = 472.09
Refractive Index 1.9-2.0; 2.6-2.7

Resources and Citations

  • R. Newman, E. Kaplan, M. Derrick, “Mopa mopa: Scientific analysis and history of an unusual South American resin used by the Inka and artisans in Pasto, Colombia,” Journal of the American Institute for Conservation 54 (2015): 123-148.
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 5957
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 200
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993