Often an oily green, prehnite may also range from pale yellowish to brown. Columnar or tabular crystals are rare: it occurs more usually as aggregates of barrel-shaped crystals or as botryoidal masses. Some pale yellowish brown prehnite is fibrous enough to be cm cabochon, and may show the cat's-eye effect.

Prehnite is found in basaltic volcanic rocks, intrusive igneous rocks, and in some meta- morphic rocks. Pale green masses are found in Scotland; dark green or greenish brown masses in Australia; aggregates of crystals in France.

Prehnite is named after Colonel von Prehn, who first introduced prehnite to Europe.