This Namibian prehnite specimen displays large, light mint green semi-botryoidal 'ball form' growths composed of masses of intergrown orthorombic crystals atop a sturdy basalt matrix alongside frosty white calcite. Much of the display face is coated with substantial growth; the largest mass of prehnite measures 43mm across and is raised upwards to about 16mm thick, and the largest calcite crystal is fully terminated to a rhomboidal form, lustrously shiny and spans to 18mm across. It is a handsome specimen from a highly desirable locality, fitting for a discerning collector.
Prehnite was not only the first South African mineral ever to be described and named, dating back to 1788, but also the first to be named after an individual, its discoverer Colonel Hendrik von Prehn, a Dutch mineralogist and governor of the Cape of Good Hope Colony. It is a hydrated calcium aluminum silicate, light mint to vivid apple green in colour with a vitreous to waxy luster, and many specimens also display an attractive luminous translucenct quality. Typically forming in botryoidal masses of orthorombic, sheaf-shaped crystals, prehnite is particularly aesthetic, often creating unique, multi-mineral compositions alongside epidote, quartz and calcite. Until relatively recently, this mineral was quite a rarity and scarce on the market, though newly found deposits have made it more available and incredibly popular among both collectors and lapidary artists. Much of the classic, desirable prehnite originates from Africa, with Namibia, Mali and South Africa being the best producers of fine collectors specimens, though Australia, China, France and Jersey in the US are also good sources of the mineral.