Aragonite (w. Malachite and Dolomite)

Chemistry: CaCO3
Size: 100 mm
Owner: Jim Robison
Photographer: John Schneider

A rich druse of off-white prismatic trillings of aragonite (var. tarnowitzite; crystals to 9 mm) occupies the concave surface of a multilayered dolomite "cast".  

Malachite appears to have crystallised selectively, accompanied by partial dissolution or corrosion of the underlying aragonite.   

The convex surface of the dolomite cast (not shown) has a botryoidal appearance, with a very thin orange-yellow veneer overlying cream-white dolomite.