Chocolate dogtooth calcite, large

Chocolate dogtooth calcite, largeLocale: Santa Eulalia, Chihuahua, Mexico Approx size: 3. 75 x 2. 25 x 2. 25" Approx weight: 485g (about 1 lb) Known by the trade name "chocolate dogtooth calcite," this type of calcite from the famed Santa Eulalia mining district grows in hedgehog clusters of sharp dogtooth (scalenohedral) crystals. The variety gets its distinctive opaque brown appearance from iron oxides; a layer of hematite included calcite is deposited on the surface during a later

Locale: Santa Eulalia, Chihuahua, Mexico

Approx size: 3.75 x 2.25 x 2.25"

Approx weight: 485g (about 1 lb)

Known by the trade name "chocolate dogtooth calcite," this type of calcite from the famed Santa Eulalia mining district grows in hedgehog clusters of sharp dogtooth (scalenohedral) crystals. The variety gets its distinctive opaque brown appearance from iron oxides; a layer of hematite-included calcite is deposited on the surface during a later phase of growth.

Broken crystals around the edge reveal the first phase of growth had some clarity with yellow-brown zoning following the crystal structure. Calcite has perfect cleavage so it is common to have a point or two that has cleaved off, leaving a flat smooth window displaying this growth. This specimen shows signs of natural etching that have left the tip of many of the dogtooth crystals blunted or hollow.

Very small crystals often dot the surface of the calcite. There is a flaky thin off-white mineral overgrowth covering a lot of the specimen, which may by calcite. Quite a few tiny points and clusters of quartz are also tucked between crystals, some with a smoky-quartz tint.

UV reactivity: the presence of iron dampens any reaction in the brown calcite, which is non-reactive. Where the strip of clear calcite is exposed along the matrix, you can get a good peachy-red reaction with some phosphorescence using 365nm UV light