Calcite 
 
Locality:  Daye Co., Huangshi, Hubei, China

Size: 75 mm x 50 mm
 
A very unusual Calcite specimen with two generations of growth. An initial scalenohedron shaped crystal (Dogtooth) with secondary Calcite that partially covered the initial Calcite growth. There is also some light reddish iron oxide on the dogtooth crystal.
 
Calcite is a carbonate mineral and a polymorph of Aragonite. It is extremely variable in colour, ranging from clear, white, yellow, orange, blue, pink, red, brown, green, black and grey.