Calcite (Dogtooth)

TruDogtooth Calcite is a crystal habit of calcite (calcium carbonate, CaCO₃) characterized by sharply pointed, elongated crystals that resemble canine teeth — hence the traditional name “dogtooth spar.” These crystals form in the scalenohedral habit, meaning they develop as twelve-faced crystals composed of unequal triangular faces (a scalenohedron). Unlike simple rhombohedral calcite, scalenohedral growth reflects specific environmental conditions that promote directional crystal elongation along the c-axis of calcite’s trigonal structure. Scalenohedral calcite forms in a wide range of geological settings, most commonly within hydrothermal veins, limestone cavities, skarn systems, and ore deposits.

It develops when calcium-rich fluids precipitate calcite under conditions of moderate temperature, open cavity space, and relatively stable chemistry. Variations in fluid composition, temperature, pressure, and trace elements can influence crystal size, transparency, and color. Dogtooth calcite may be colorless, white, honey-yellow, amber, green, brown, or smoky depending on inclusions or trace impurities such as iron, manganese, or organic material. This habit is especially well developed in hydrothermal ore environments where large open cavities allow unrestricted crystal growth. Scalenohedral calcite is frequently associated with quartz (SiO₂), fluorite (CaF₂), galena (PbS), sphalerite (ZnS), and pyrite (FeS₂).

Notable world-class occurrences include deposits in Hunan Province, China, Elmwood Mine (Tennessee, USA), Sweetwater Mine (Missouri, USA), Freiberg, Germany, and various Mexican and British carbonate-hosted ore districts. Collector interest in dogtooth calcite centers on crystal sharpness, luster, transparency, and association with contrasting matrix minerals. Large, undamaged scalenohedrons with high clarity and strong termination are particularly prized. Because scalenohedral growth requires open space and stable fluid conditions, fine examples often originate from well-developed vein or cavity systems within mineralized zones.