Dioptase

specimen number:
2013507

location:
Reneville, Pool, Republic of Congo

description:
Attractive green crystals of dioptase measuring to 1.5 cm in size forming a cluster without matrix. In good condition.

Reneville, located in the Pool Region of the Republic of the Congo, is a world-renowned mineral locality situated within the West Congolian Belt. Geologically, the deposit consists of secondary copper mineralization hosted in Neoproterozoic sedimentary rocks, specifically within the carbonate-rich Schisto-Calcaire Group. The primary ore was subjected to intense tropical weathering, which oxidized original copper sulfides and redistributed the metals into karst-related fractures and solution cavities. Historically, Reneville became famous in the early to mid-20th century, particularly during the French colonial period, as a source of spectacular mineral specimens rather than as a large-scale industrial mine. Dioptase is the most iconic mineral from this site, occurring as intense, emerald-green cyclosilicate crystals that are prized for their exceptional color and sharp rhombohedral habit. These crystals often reach sizes of several centimeters and are frequently found growing on a contrasting matrix of white quartz or pale plancheite. While other localities like Tsumeb produce similar minerals, Reneville dioptase is distinctive for its dark, "forest-green" saturation and the high luster of its crystal faces. Today, specimens from the historic Reneville diggings remain some of the most sought-after copper silicates in the international mineral market, representing a classic African locality for the species.

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