prehn·​ite | \ˈprāˌnīt, ˈpreˌ-\
plural -s

Definition of prehnite 

: 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)

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History and Etymology for prehnite

German prehnit, from Colonel Van Prehn 18th century Dutch officer who brought it from the Cape of Good Hope + German -it -ite entry 1

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