"Rock of the Month # 132, posted for June 2012" ---

Mimetite, ideal formula Pb₅(AsO₄)₃Cl), is a monoclinic lead arsenate, calculated specific gravity 7.305. Figured sample from Shaft 11, Touissit mine, 4 km from the Algerian border.

Sphaerocobaltite is the colourful, shocking-pink carbonate of cobalt, rhombohedral CoCO₃, calculated specific gravity 4.208. The figured specimen from Agoudal, 25 km east of Bou Azzer. It occurs on a mixture of densely fine-grained quartz and crystalline calcite.

Cerussite is orthorhombic lead carbonate, PbCO₃, colourless to pale yellowish with adamantine to vitreous lustre, calculated specific gravity 6.577. It forms simple tabular crystals, but also often appears as contact- and penetration twins, repeated to form six-rayed stellate groups (Dana, 1932, pp.524-525). The figured samples are from a specimen mine 3 km south of Mibladen, notable also for vanadinite.

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)

The Touissit area contains a belt of deeply-oxidized lead-zinc deposits near the eastern (Algerian) border of Morocco (see the fine new, detailed review by Jahn and Bode, in the November 2013 issue of the Mineralogical Record). The French mined the deposits for several decades after World War I, but only in the late 1970s did the "Touissit" area start producing superb specimens of azurite, anglesite, white aragonite (the variety known as tarnowitzite), wulfenite and other minerals, including many secondary minerals produced in the weathering process. Mimetite crystals occur in epitaxial overgrowth on barrel-shaped arsenic-rich vanadinite (ibid., pp.635-636) and apparently, "mimetite from Touissit has been known for a long time, but specimens of it are seldom seen". Mimetite was found in the late 1980s as pale yellow spherical aggregates, on spherical masses of malachite, sometimes with azurite or limonite in colourful assemblages.

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 from Morocco.

References

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.

Jahn,S and Bode,R (2013) The Touissit-Bou Beker mining district, Morocco. Mineral.Record 44, 595-651.

Jensen,M (1982) Endlichite and descloizite from the Chalk Mountain mine, Churchill County, Nevada. Mineral.Rec. 13 no.4, 219-221.

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 (1980) Famous mineral localities: Los Lamentos, Chihuahua, Mexico. Mineral.Record 11 no.5, 277-286.

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.