During the late eighteenth century, the southern most tip of Africa was a Dutch Colony, centered around the Cape of Good Hope. Prehnite was found by Hendrik Von Prehn (1733-1785) during his time as commander of the military forces of the Colony from 1769-1780. Von Prehn, like many other aristocratic men of his time, was well educated in languages and interested in the natural sciences, including geology and mineralogy. Correctly believing that he had found a new mineral, he brought back an example of the green stone to Europe where it was analyzed by the German geologist, A.G. Werner (1749-1817). In 1788, Werner officially determined that Prehnite was a new mineral and named it after its discoverer, who had recently passed away. This marks the first known instance of a mineral being named after a person.
Occasionally, Prehnite is marketed under the name of “Cape Emeralds.” This strategy cashes in on the higher name recognition and drives the price up, much in the same way that Prasiolite may be marketed as “Green Amethyst”. But Prasiolite and Amethyst are essentially the same mineral, the only difference being color. Prehnite and Emerald, are both green, but are otherwise completely distinct minerals.