aragonite crystal cluster - hand/display specimen from the Fès-Meknès region of Morocco

Aragonite - CaCO₃

Tazouta Mine, near Tazouta, Sefrou Cercle, Sefrou Province, Fès-Meknès Region, Morocco

Aragonite, a polymorph of calcite, has the same composition as calcite but crystallizes in the orthorhombic system, while calcite forms trigonal crystals.

Aragonite has three habits of crystallization, either forming radiating groups of fine to coarse crystals, as tabular crystals or as pseudohexagonal twins as in these examples. Single crystals are usually tabular plates or long slender needles.The crystals in these clusters are formed by an intergrowth of three individuals twinned on the prism face and are not true hexagonal forms. They radiate from a common center.

The aragonite clusters at this mine are found in a layer of reddish clay and come out as mudballs. Since the area of the mine is dry, the mudballs are taken to a local river and washed. The reddish color is a hematite stain. 

Aragonite was named in 1797 by Abraham Gottlob Werner, German mineralogist, for the type locality, the village of Molina de Aragón, Spain, and not the province of Aragón, as has been reported in error.

The bust of Werner is in a park in Freiberg, Germany, where Werner had been a professor at the Mining Academy. Having never seen active volcanism, Werner thought all rocks were deposited from water, a theory called Neptunism. The only basalt he had seen, a columnar basalt at Stolpen, was sandwiched between beds of limestone, so to Werner, the basalt was also precipitated from water. 

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