Erythrite from Morocco

(Bou Azzer mine)

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Above: Two specimens displaying erythrite as (left) sprays of coarse prisms on dark and highly altered serpentinite and (right) fine mm-scale crystals in a cavity on goethite-stained host rock. Samples from the Irwin Kennedy collection, purchased at Bou Azzer, February-March 2012.

"Rock of the Month # 133, posted for July 2012" ---

Erythrite, or "cobalt bloom", is a characteristic mineral of the Bou Azzer mining camp, the cobalt derived from the assemblage of nickel- copper- cobalt sulphide ore minerals developed in the ultramafic host rocks. Erythrite is a cobalt arsenate, ideal formula Co3(AsO4)2.8H2O. Although it may form striated prismatic crystals, it is most often encountered as dull pink, dusty encrustations. In contrast, Bou Azzer has yielded the world's finest specimens of crystalline erythrite, from Vein 7 and other sites within the mining camp (Favreau et al., 2007). Erythrite has a nickel analogue in the green secondary mineral annabergite. It is found in numerous mining camps with cobalt-rich ores, including: Schneeberg (Saxony, Germany); Tunaberg (Sweden); some of the mining districts of Cornwall in England; and Cobalt (Ontario, Canada: Dana, 1932, p.722).

Minerals of Morocco

There is a long history of mining in the area of the eastern Anti-Atlas mountains. The Imiter district has produced many specimens of silver minerals and associated species, including native silver and proustite, acanthite, galena, cinnabar, imiterite (Ag2HgS2), lavendulan (a blue arsenate of sodium, calcium and copper), mimetite and polybasite (Barral et al., 2011). The Bou Azzer district is known for at least 215 mineral species (Favreau et al., 2007). The diversity is due to chemically diverse metallic ores weathering to a plethora of secondary salts. There are ores of cobalt and nickel, with traces of bismuth, arsenic, tungsten, molybdenum, etc. Minerals include azurite, brochantite, pink cobaltian calcite, aragonite, celestine, gersdorffite, goethite, magnetite, scorodite, coarse skutterudite crystals in calcite (Tamdrost mine), sphaerocobaltite on quartz (from Agoudal), stichtite and more.

A variety of Moroccan mineral species recur as fine specimens at mineral shows year after year. Victor Yount was a pioneer in the marketing of Moroccan specimens (Moore, 2012). Notable Moroccan minerals, illustrated in the pages of Mineralogical Record in particular, include:

  • Acanthite from Imiter (Moore, 2005; Polityka, 2005)
  • Anglesite from, e.g., Touissit (Wilson et al., 1992; Wilson, 1988, 2011)
  • Azurite from Touissit (Wilson et al., 1992; Larson, 2010)
  • Cerussite, such as snowflake cerussite from Taouz (Larson, 2004)
  • Erythrite (Moore, 2000; Larson, 2010; Wilson, 2011)
  • Fluorite (Larson, 2010)
  • Malachite (see azurite, e.g., Larson, 2010)
  • Mimetite (Barral et al., 2011).
  • Silver (native Ag and other Ag minerals from Imiter: Barral et al., 2011)
  • Skutterudite (Trinchillo, 2008)
  • Sphaerocobaltite (cobaltian calcite or cobaltocalcite, cobalt carbonate, from Bou Azzer: Larson, 2004; Wilson, 2009; Moore, 2012)
  • Vanadinite from, e.g., Mibladen (Wilson et al., 1992; Moore, 1998; Scovil et al., 2001; Trinchillo, 2008; Wilson, 2011)

Acknowledgements. With thanks to Irwin Kennedy and Wanda Zyla, whose peregrinations have brought to light numerous fine mineral specimens, and extended knowledge of some far-flung mineral localities. Other examples of their material on these pages are: calcite from Mexico and galena with orpiment from Peru, as well as vanadinite and other minerals from Morocco.


Barral,J-P, Favreau,G and Lheur,C (2011) Imiter: Morocco's greatest silver mine. Mineral.Record 42, 107-135.

Dana,ES (1932) A Textbook of Mineralogy. John Wiley and Sons, Inc., New York, 4th edition, revised by Ford,WE, 851pp.

Favreau,G, Dietrich,JE, Meisser,N, Brugger,J, Haddouch,LA and Maacha,L (2007) Bou Azzer, Morocco. Mineral.Record 38, 345-407.

Larson,B (2004) Sainte-Marie aux Mines show 2003. Mineral.Record 35, 145-148.

Larson,B (2010) Sainte-Marie-aux-Mines Show 2010. Mineral.Record. 41, 541-546.

Moore,T (1998) Tucson Show 1998. Mineral.Record 29, 209-221.

Moore,T (2001) Denver Show 2000. Mineral.Record 32 no.1, 56-63.

Moore,T (2005) Munich show 2004. Mineral.Record 36, 117-121.

Moore,TP (2012) Victor Yount and his calcite collection. Mineral.Record 43, 85-97.

Polityka,J (2005) Springfield show 2004. Mineral.Record 36, 109-113.

Scovil,J, Larson,WF and Polityka,J (2001) What's new in minerals. Mineral.Record 32, 487-497.

Trinchillo,D (2008) The Marc P. Weill collection of fine minerals. Mineral.Record 39 no.1, supplement, 96pp.

Wilson,WE (1988) What's new in minerals? Mineral.Record 19 no.3, 209-218.

Wilson,WE (editor) (2009) Private Mineral Collections in Texas. Mineral.Record 40 no.1, supplement, 180pp.

Wilson,WE (editor) (2011) Private Mineral Collections in Italy. Mineral.Record 42 no.1, supplement, 144pp.

Wilson,WE, Bartsch,JA, Van Pelt,H and Van Pelt,E (1992) Minerals of the Houston Museum of Natural Science. Mineral.Record 23 no.1, supplement, 34pp.

Graham Wilson, 13 May 2012

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