Malachite after Azurite

specimen number:
5003459

location:
Shaft IX, Touissit, Jerada, Oriental, Morocco

description:

A thick prismatic terminated crystal of what was once azurite 5.5 cm in height coming beautifully off matrix and replaced by green crystallized malachite. Classic stuff from this locality. Complete all around and in great condition. This was collected in 1981.

Touissit, located in northeastern Morocco near the border with Algeria, is a historic mining district renowned for its rich polymetallic deposits. Mining activities began in the early 20th century, specifically around 1908, driven by the extraction of high-grade lead, copper, and zinc ores hosted within sedimentary carbonate sequences. Geologically, the deposit is a classic Mississippi Valley-type ore body, where metal-bearing hydrothermal solutions migrated through permeable strata and precipitated extensive sulfide mineralization. Mineralogically, the district became world-famous among collectors for producing magnificent, highly lustrous specimens of anglesite, cerussite, and azurite before large-scale industrial operations wound down toward the end of the 20th century.

Pseudomorphs involving malachite after azurite occur when copper carbonate hydroxide in the form of azurite is chemically altered and replaced by malachite, which shares a similar chemical composition but possesses a different crystal structure. During this secondary alteration process, circulating solutions rich in carbonate and water react with the existing azurite crystals, gradually transforming the interior while preserving the original external crystal geometry. The resulting specimens are highly prized by collectors for displaying the sharp, distinct crystal shapes of azurite combined with the vibrant green color and velvety or earthy texture of malachite.

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