This silver on calcite is from Batopilas in the Andres del Rio District, Chihuahua, Mexico. It consists of a calcite matrix that is sandwiched between viens of acanthite.This location has been mined since 1632 when the conquistadores first started exploiting the deposits. Production continues to this day. The locale is well known for the prodigious amount of world class mineral specimens found there. Acanthite is an associated mineral. it is a sulfide mineral containing the elements Ag and S. The host matrix is white calcite That hosts silver in the form of crystals, wires, and complex crystal formations. There are also some micro spinel twins and some micro cubes. This piece measures 1 1/8 x 1 1/8 x 15/16 inches or 28 x 28 x 23 mm.