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It's pronounced with a short 'e' and a long 'i': preh-night.
Babington, Westfield,
Tourmaline, Chesterfield,
Prehnite, Westfield,
Prehnite is a silicate mineral unto itself, and is not a member of the quartz grouping.
Diamonds, obsidian, prehnite, and the minerals of the zeolite group are formed from volcanic processes.
Emerald, Malachite, and Chrysoberyl etc
Reference: What_minerals_are_used_to_make_a_bright_green_color_or_special_effect