Vivianite
Richmond, Virginia
This specimen measures 8.5cm in diameter
Vivianite Fe3(PO4)2.8H2O
Phosphate; hydrous phosphate of iron
Color and Luster: Blue, green; colorless when fresh, becomes dark blue upon exposure to light; dull, vitreous, pearly on cleavage; streak white, blue, greenish blue
Hardness: 1.5-2
Cleavage: Perfect, one direction
Fracture: Splintery, earthy, sectile, thin flakes flexible
Crystals: Monoclinic; usually in short to long prismatic crystals; also radial fibrous, earthy
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals