Calcite rafts

Calcite crystals precipitate in this highly localized environment and attach to one another to form what appear to be rafts of a white material.

Limestone caves provide a favorable environment due to little air movement and water containing significant concentrations of calcium and carbonate ions.

X-ray diffraction analysis showed that the floating solid material was greater than 97 percent calcite.

Scanning electron micrographs confirmed that the shape of the crystalline material was rhombohedral, which is consistent with calcite crystal formation.

[7][8] Micro calcite rafts have been observed on (soda) straw stalactites solution drops suspended beneath concrete structures.

[9] They are derived from concrete, lime or mortar, and mimic the shapes and forms of speleothems created in caves.