Calcite twins from the old finds at Areponepuchic were historically known since the early 1900s and have remained an iconic style of calcite for any calcite or Mexican collection, unique to old eras of mining. They are immediately recognizable. Most are singles of small or large size, which stand on the points like arrowheads for display. This, however, is a very rare cluster of two twins, each translucent to transparent! Note that it is naturally antique-looking, cleaned only with water and not modern lab cleaning that might make it bright and shiny and more lustrous. This is how it was found, washed with water, probably nearly a century ago. The sharp crystals, quality of shape and clarity, and the cluster form all make this exceptional for a surviving example of what was once a must in ever sophisticated collection of the 1950s-1980s generation of collectors. Additionally, it was an old piece from Harvard's museum, deaccessioned in 2005. It was later in the Evan Jones collection of Mexican minerals, which he later sold to focus on Arizona minerals. This is a very rare historic twinned calcite and one of only several in such good condition we know to still exist.