prehnite
noun
prehn·ite
ˈprāˌnīt,
ˈpreˌ-
plural -s
: a pale green mineral Ca2Al2Si3O10(OH)2 that occurs in crystalline aggregates having a botryoidal or mamillary structure but only rarely in distinct crystals and that is a basic calcium aluminum silicate (hardness 6–6.5, specific gravity 2.80–2.95)
Word History
Etymology
German prehnit, from Colonel Van Prehn 18th century Dutch officer who brought it from the Cape of Good Hope + German -it -ite entry 1