Dogtooth calcite also known as dog-tooth spar is a speleothem or cave formation. This distinctive mineral is often made up of large crystals which can be very sharp. The name "dogtooth" calcite came about because some crystals can look similar to dogs' teeth.
The crystals in dogtooth calcite grow very slowly over long periods of time in large open cavities often underground in limestone caves. They can also be found in veins, fractures and geodes. It takes billions of 'unit cells' to form one visible crystal.
Speleothem comes from the Ancient Greek word for 'cave deposit'. The formations which include stalactites, stalagmites and many others form through precipitation. When minerals dissolved in water are left behind after the water dries up, they 'precipitate' out of the solution. A layer of crystalline calcite lies beneath the top layer of the crystals in dogtooth spar.
Zoom in even closer and see more detail in this dogtooth spar mineral by visiting our page on Flickr.