Calcite

The José María Patoni mines in the San Juan del Río Municipality of Durango, Mexico, are known for just one species, Calcite.  The occurrence is famous for the quality and variety of crystal habits and this superb small miniature is an excellent example of butterfly twins.  The colourless Calcite is tinged slightly milky white and forms a cluster of intergrown twins, the largest of which measures 2.7 cm across at its widest point.   These are true butterfly twins, not slightly distorted heart twins which are commonly misnamed.  Viewed under a loupe the surface texture is slightly etched with micro pit marks, giving the Calcite a satin lustre.  Under LWUV the Calcite fluoresces pale straw to lemon yellow.  A lovely example of a Calcite butterfly twin from José María Patoni.