1/2 pound lots of mine rough Prehnite from Mali,Africa in bigger 1 to 3 inch sized pieces.Each lot will be randomly scooped from material as pictured and lotted into 1/2 pound lots.Color is green/ yellow green with some random darker black and brown epidote crystal and runs from translucent to opaque.Prehnite is a inosilicate of calcium and aluminium with the formula  Ca2Al(AlSi3O10)(OH)2. Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite.It is brittle with an uneven fracture and a vitreous to pearly lustre. Its hardness is 6-6.5,and its color varies from light green to yellow, but also can be colorless, blue or white.It is mostly translucent, and rarely transparent.Lots generally contain 3 to 7 pieces.