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. The prehnite in this specimen is a crust on parent rock. So it displays on the one side. This fun little yellow specimen has the pearly luster. It looks a lot like smithsonite. This specimen comes from Southbury Connecticut.