Flowstone is perhaps the most common of all cave deposits and is almost always composed of calcite or other carbonate minerals. It forms in thin layers which initially take on the shape of the underlying floor or wall bedrock beneath but tends to become rounded as it gets thicker. Flowstone masses are often fluted with draperies at their lower end, such as the area above the caver’s head. Impurities in the calcite may give a variety of colors to flowstone, such as the reddish or orangish areas (likely due to iron) in some of the photos.

Flowstone forms from actively flowing water (rather than water squeezed through cracks) in which carbon dioxide is lost, and carbonate material is deposited. This is the basic mechanism forming stalagmites or stalactites as well, and the these often form together.

Continuous flowstone deposits may cover vast areas of a cave floor or flow for hundreds of vertical feet down the side of vertical shafts. Ft. Stanton Cave in New Mexico has a continuous flowstone deposit on the floor of an intermittent cave stream, which measures miles long and exceeds anything else known. Its noted and pictured on the page on the legacy Virtual Cave site devoted to the world’s largest speleothems. It also has photos of one of the tallest vertical flowstone mass reported in a cave.

AUTHOR: Dave Bunnell