Prehnite is a translucent to transparent gem-quality hydrated calcium aluminum silicate. It was the first mineral to be named after an individual, and it was also the first mineral to be described from South Africa, long before South Africa became one of the most important sources for precious and semi-precious gems. It was first described in 1788 after it was discovered in the Karoo dolerites of Cradock, South Africa. Prehnite was later named after its discoverer, Colonel Hendrik von Prehn (1733-1785), a Dutch mineralogist and an early governor of the Cape of Good Hope colony.
Until recently, prehnite was a rare collector's gemstone, but new deposits have now made it more readily available. In China, prehnite is sometimes referred to as 'grape jade' owing to its typical nodule formations which often resemble a bunch of grapes. Its colour is usually a soft apple-green, which is quite unique to prehnite, but it can also occur in rarer colours including yellow, orange and blue.
Primary deposits of prehnite are sourced from several locations around the world. Some of the most important deposits come from Africa (Namibia, South Africa), Australia (Western Australia, Northern Territory), Canada, China, Germany, Scotland, France and the United States (New Jersey, Pennsylvania and Virginia). Rare, orange coloured prehnite has been discovered in South Africa. Quebec, Canada is known to produce prehnite with distinct, individual crystals. REF: Geologylearn Blogspot