prehnite

[prey-nahyt, pren-ahyt]

noun

a mineral, hydrous calcium aluminum silicate, Ca2Al2Si3O10(OH)2, occurring in light-green reniform aggregates or tabular crystals.

Origin of prehnite

1785–95; named after Col. Van Prehn, 18th-century Dutchman who brought it from South Africa to Europe; see -ite¹

Also, in detached fragments, on the south shore of Lake Superior, intimately mixed with prehnite.
Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River, in 1820
Henry Rowe Schoolcraft
Prehnite, pren′īt, n. a hydrous silicate of alumina and lime, usually of a pale-green colour.
Chambers's Twentieth Century Dictionary (part 3 of 4: N-R)
Various