Prehnite was the first mineral to be named after a person—Colonel Hendrik von Prehn, a Dutch mineralogist and governor of the Cape of Good Hope in the 1700s.

Prehnite usually forms in cavities of volcanic rocks—especially basalts and andesites—and is commonly associated with minerals like zeolites, calcite, epidote, and quartz. You’ll often find it as botryoidal (grape-like) clusters, tabular crystals, or stalactite forms.

Prehnite is used as a gemstone, it is typically pale green, yellow-green, or apple green. Can also be white, gray, or colorless.