Dims: 1.7" x 1.6" x 1.1" (4.3 x 4.1 x 2.8 cm)
Wt: 1.89 oz. (53.7 g)
Naica, Chihuahua, Mexico
A bit of a mystery surrounds this specimen. It consists of a cluster that is made up predominantly of Calcite. The Calcite occurs in the form of rhombohedrons that range in size from 1 mm to 0.5" (1.3 cm) along an edge. Their color is a bright white and their luster is pearly, which makes me think that maybe these are actually crystals of ankerite, as there are also many tiny clusters of "dogtooth" Calcites scattered on parts of some of the large crystals. That is not the mystery, though. Among these large crystals, the tiny "dogtooth" crystals, and many small disphenoidal chalcopyrites that are scattered about, are some thin, bladed crystals that I cannot identify. They have what appears to be a monoclinic form, a pale beige color and a vitreous luster, and are transparent and very clear. They show no effervescence in a dilute acid, and seem to be harder than Calcite. I thought they might be siderites at first, but the form is wrong. I really am at a loss as to what they are.