Chocolate dogtooth calcite, large

Chocolate dogtooth calcite, largeLocale: Santa Eulalia, Chihuahua, Mexico Approx size: 4 x 3 x 2. 5" Approx weight: 652g (about 1 1 3 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: 4 x 3 x 2.5"

Approx weight: 652g (about 1 1/3 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 reveal the first phase of growth had some translucency with yellow-brown zoning in the interior. 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 has left the tip of many of the dogtooth crystals blunted or hollow. Very small crystals often dot the surface of the calcite. A lot of the specimen is covered with a flaky thin off-white mineral overgrowth, which may by calcite. Tiny points of quartz often spot these specimens; this piece has a disc-like botryoidal quartz formation on one calcite crystal, with two small quartz points growing off it.

UV reactivity: the presence of iron dampens any reaction in the brown calcite, which is non-reactive. This piece has limited reaction.