3.6" Blue Veszelyite Crystals on Botryoidal Hemimorphite - Congo

Veszelyite is a rare secondary copper and zinc mineral found in the oxidation zones of base metal deposits. Veszelyite crystals are typically emerald green, blue or a mixture of the two. They can be found as small, lustrous clusters peppered across other minerals or as crusts, but in rare cases they can also be found as dense crystal aggregations.

Veszelyite specimens from a recent (2019/2020) find in the Bouenza Department of the Republic of the Congo (Brazzaville) are a perfect example of this rare instance of dense aggregations of veszelyite. Within the hemimorphite zone of the Palabanda Quarry, irregularly dispersed formations of this rare mineral were unearthed. They occurred in small brecciated/weathered cavities where most of the veszelyite formed as crusts, while some spots revealed well formed crystals over hemimorphite. The area that contained these crystals was mined over five months, the final two of which appeared to indicate that the pocket was completely exhausted.

Hemimorphite is a basic hydrous zinc silicate with the chemical composition Zn4Si2O7(OH)2 · H2O. It earned its name from the Greek terms that best define its crystal structure. It has two different terminations on each side of the crystal, hence the inclusion of the greek terms "hemi", meaning half, and "morph", meaning shape. The crystal formations can range anywhere between a crystal druze or botryoidal formation to radiating acicular crystals and more. Hemimorphite has been found in shades of white, beige, light brown, and a bright, electric blue. It can also form as yellow and green crystals on rare occasions.

Prior to 1803, hemimorphite and smithsonite were thought to be the same mineral, called "calamine". However, further scientific research concluded that these were two distinct minerals.