Prehnite is a hydrated calcium aluminum silicate. Prehnite comes in a nice medium apple green and progresses down to a light greenish yellow. It may also be a brownish yellow. Prehnite is fairley durable having a hardness of 6 to 6.5. Prehnite may have a luminous quality, as it's luster is vitreous to pearly. Originally found in south Africa, Prehnite is now found several other locations. such as USA, Australia and China. This is a very nice green plate of Prehnite with lots of sparkling clear Quartz Crystals. This specimen is in great shape.