Calcite (Inventory)/Spar/dogtooth

From LagWiki

Dogtooth spar

The dogtooth field should be used to list stations which exhibit dogtooth spar crystals.

Dogtooth spar is a crystaline speleothem usually of calcite. The shape is scalenohedral -- triangular facets -- with pointed ends. The size can vary from barely discernable to quite large. The color can vary too. Often only one end of the scalenohedron may be visible giving each crystal a pyramid-like shape. Sometimes, both ends of the crystal can be seen forming a kind of faceted football shape. They can occur singularly or in clusters. They can often be found lining the insides of vugs or cavities and cracks but can also occur on the ceiling or walls directly. Since they formed when the cave was phreatic, they can be obscured by other formations such as flowstone, popcorn, crusts or staining. When looking for dogtooth spar, take the time to look into cracks and vugs in the walls, floor and ceiling. And don't forget to examine breakdown -- it may possess a vug containing dogtooth spar. Often when dogtooth spar is found, it can be found at nearby stations, too.

If the shape of each crystal does not seem to be scalenohedral but is more complex, you may be seeing nailhead spar.

References

Hill, Carol; Paolo Forti (1997) Cave Minerals of the World (Second Edition ed.) National Speleological Society p 101 ISBN: 1-879961-07-5
Palmer, Arthur N. (2007) Cave Geology CAVE BOOKS, Dayton, OH p 275 ISBN-13: 978-0-939748-66-2, ISBN-10: 0-939748-66-5