Prehnite

Prehnite is a recognised mineral species best known for its soft green, yellow-green and occasionally colourless appearance. It commonly forms as rounded, botryoidal, globular or fan-like aggregates, although well-formed crystals can also occur. Prehnite is a calcium aluminium silicate hydroxide and typically develops in low-temperature hydrothermal environments, particularly in cavities and fractures within basaltic and other volcanic rocks. It is often found alongside minerals such as Calcite, Epidote, Zeolites, Quartz and Native Copper. Its translucent green appearance has made it popular as a gemstone and ornamental material, especially in cabochons, beads, spheres, carvings and polished freeforms. Prehnite was named in the late 18th century after Hendrik von Prehn, a Dutch military officer and mineral collector who brought specimens from South Africa to Europe. The mineral’s classic type locality lies within the Karoo dolerites of the Eastern Cape, South Africa. Although pale green is the colour most often associated with Prehnite, natural specimens may also be colourless, white, grey, yellow, pale brown or very rarely pale blue.