Calcite with Sphalerite

If I were to pick my favorite top 5 localities Naica would be in that selection. The fluorites and calcites in particular. This piece is all about the calcite. It is complete all around (all contact at the bottom)and exhibits 4 dominant rhombohedra that overgrew prior rhombohedra . They are offset by jet black sphalerites. Formerly in the Mary and Gardner Miller collection, they must have been as enamored as I with the subtlety of the composition. Incredible reactivity to LW reveals some manganese content.

Locality: Naica Mine, Naica, Municipia de Saucillo, Chihuahua, Mexico

Composition: calcium carbonate