3.5" Cerussite Crystals on Botryoidal Hemimorphite - Congo

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.

Cerussite is a lead-carbonate mineral with the chemical formula PbCO3, and is an important ore of lead. It is a common weathering product of galena, explaining why it is typically extracted from oxidized zones of lead ore deposits. It can form into a variety of different structures, sometimes in fibrous patterns and other times in granular aggregations, though it generally forms vitreous pseudo-hexagonal crystals. Its colors vary depending on composition and structure: it is most commonly colorless, white, grey and green-tinted.