Chrysocolla pseudomorph with Malachite, Quartz

specimen number:
9505326

location:
Tenke-Fungurume, Kolwezi, Lualaba, DR Congo

description:

From recent find in the Congo, prismatic crystals of what were likely azurite or barite, even possibly gypsum, to 4.5 cm in length now replaced by bright blue chrysocolla. These are extra nice as the chrysocolla is then coated with a sugary sparkling micro quartz. In very good condition for one of these, minor green malachite present as seen.

The Tenke-Fungurume mining district, located in the Lualaba Province of the Democratic Republic of the Congo, is one of the worlds largest sediment-hosted copper and cobalt producers. Geologically, the deposits are situated within the Neoproterozoic Katanga Supergroup of the Central African Copperbelt, specifically hosted in the Roan Group rocks that underwent significant folding, faulting, and tectonic thrusting during the Lufilian Orogeny. The rich ore bodies feature deep supergene enrichment zones containing malachite, heterogenite, and chrysocolla overlying primary sulfide mineralization. Historically, indigenous artisanal mining preceded formal European exploration and prospecting in the early 20th century, followed by decades of interrupted development before modern large-scale industrial open-pit operations expanded rapidly in the 21st century.

A pseudomorph occurs when one mineral replaces another while preserving the original crystal shape of the earlier mineral. In the specific case of chrysocolla on malachite after azurite, a three-step mineralogical transformation takes place. First, primary azurite crystals form. Next, hydrothermal or supergene alteration transforms the azurite into malachite, creating a malachite pseudomorph after azurite. Finally, copper- and silica-rich solutions deposit a coating or complete replacement of chrysocolla over or through the malachite matrix, resulting in a complex pseudomorphic specimen showcasing successive mineral replacements.

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