The prehnite donuts are 3cm in diameter; the light green gemstone donuts have inclusions of Hornblende.
In modern stone healing according to Michael Gienger, prehnite is highly valued for its effect of strengthening the acceptance of oneself and one's fellow human beings. Unpleasant truths can be accepted more easily with the help of this stone.
The mineral Prehnite received 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 prehnite are cape chrysolite and cape emerald, earlier common names are aedelite, chiltonite, coupholite and edelite.