Prehnite, named after Colonel Hendrik von Prehn who discovered it. It is phyllosilicate of calcium and aluminium. Prehnite crystallizes in the orthorhombic crystal system. It is brittle with an uneven fracture and vitreous to pearly luster. Its color varies from light green to grey or white. It is translucent.
The specimen is about 3.375 x 2.0 inches. It weights 7.7 oz. The color is light green and has an cloud like appearance.