The small Tumbled Stones are about 4-6mm thick and about 5-10mm long. The total length of the strand of green Prehnite is about 40cm.
The mineral Prehnite got its name after Colonel Hendrik von Prehn (1733 - 1785); spellings like Phrenite, Prenhite, Prenith or Phrenite are therefore not correct. Von Prehn brought back samples from the Cape of Good Hope in 1783 and had them examined by the mineralogist Abraham Gottlob Werner. The latter described the material and named it after von Prehn then Prehnite. The stone is the first mineral that is named after a person.
Trade names for the Prehnt are cape chrysolite and cape emerald, earlier common names are aedelite, chiltonite, coupholite and edelite.