Anthodites in Skyline Caverns
November 24, 2009
Photographer: James Van Gundy
Summary Author: James Van Gundy
Anthodites are a relatively rare mineral formation found only in certain caves, such as Skyline Caverns near Front Royal, Virginia. They're normally nearly pure white in color and usually consist of radiating bunches of needle-like crystals of calcium carbonate. Their mode of formation is not well understood, but they presumably form in air-filled chambers by the slow precipitation of calcium carbonate from thin films of water that are held to their surface by capillary attraction.
Most anthodites are composed of the mineral calcite, which is the variety of calcium carbonate that’s thermodynamically favored at the temperatures and pressures usually found in caves. Aragonite, another mineral with the same chemical formula but different crystalline structure, has greater stability at higher temperatures and pressures. Anthodites may consist of calcite, aragonite, or a combination of the two. Rarely, other minerals may be involved. Why aragonite forms at all in caves is somewhat of a mystery, but its deposition appears to be favored when the concentration of a magnesium ion is elevated in the depositing water. Skyline Caverns is the only cave system in the U.S., viewable by the general public, where anthodites can be observed. These caverns contain a number of large and showy examples of this exceptional and beautiful mineral form. Photo taken on January 28, 2008.
Skyline Caverns coordinates: 38° 53' 59.27" N, 78° 12' 54.02" W