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"Pretty in Pink"
Dave Babulski, Ed.D.
Chemistry: Co3(AsO4)2-8(H2O)
("Tips and Trips", Vol. XXXIV/nine, September 2005, page 6.)


One of the striking aspects of the mineral world is the large variety of colors that minerals present. One of the most striking of these colors is the pink to red of the cobalt arsenate hydrate mineral erythrite. Cobalt deposits often feature erythrite as a secondary mineral from alteration of the primary cobalt minerals such as the siegenite (cobalt nickel sulfide) and linnaeite (cobalt sulfide). This mineral is called "Cobalt Bloom" by miners and is used to indicate the presence of cobalt ore minerals. Its pink to red color is distinctive and stands out against the drab coloration of the host rocks. The mineral gets its name from the Greek, erythros for "red".

From the micromounters perspective erythrite is somewhat rare but produces striking specimens. At mineral shows, I have found that this mineral fetches a princely sum for really good micromount specimens. In micro form the mineral forms flattened monoclinic form plates, usually a transparent pink or red color. As the crystals become larger, the mineral becomes less transparent and deeper in color. It is interesting that erythrite forms a solid solution series with the nickel arsenate annabergite. The crystal form for both minerals is almost the same. The photograph shown below is of erythrite from the Aghbar Mine, Bou Azzer, Anti-Atlas Mountains, Morocco. The mineral was photographed through the microscope at a magnification of 30X with Fuji ASA 200 color print film using a white LED as the light source and a 4 second exposure.

Although good micromount specimens of erythrite are a bit hard to come by, the beauty and unique color of the mineral makes a must have for the micromount collection. I have found that the easiest specimens to obtain and that have good micromount potential are those form the Bou Azzer area of Morocco.

Until next time may all your skies be blue and may all your vugs be crystal filled.


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