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Smithsonian National Museum of Natural History


Photograph of a triple dogtooth of calcite (NMNH R19423) from the National Mineral Collection
Photo by Chip Clark. Click to zoom.
Catalog Number NMNH R19423-00
Locality Rio Grande Do Sul, Brazil

Calcite is a very common carbonate mineral that is widespread and found in many forms and colors. It is typically colorless or white, however due to impurities it can occur in shades of red, yellow, orange, green, blue, violet, brown, and black and can be multicolored or banded. Its crystal shape is commonly rhombohedral and scalenohedral, but can also form as tabular, acicular, prismatic or needle-like crystals. Found in most geologic settings in one form or another, it is most common as massive material in limestones and marbles.This specimen is a triple dogtooth calcite. Dogtooth calcite forms as a grouping of scalenohedral crystals resembling dogs’ teeth, often occurring in caves or environments where the crystals can grow in an open space, like cavities forming geodes.


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