Mineral: Conichalcite, Calcite
Chemistry: CaCu2+(AsO4)(OH)
Size: 75 mm
Owner: Chris Amo
Photographer: John Schneider

Rhombohedral crystals of colourless-white calcite (to 40 mm), richly encrusted (and included by) spherules of vivid lime-green conichalcite (to 2 mm).

Later, partly-formed rhombs of colourless calcite clearly post-date (overgrow) the conichalcite, indicating an alternation in the solution chemistry that allowed alternating crystallisation of these two minerals.