IvyBlock

Bentonite (/bntnat/)[1][2] is an absorbent swelling clay consisting mostly of montmorillonite. It usually forms from weathering of volcanic ash in seawater,[3][4] which converts the volcanic glass present in the ash to clay minerals. Bentonite beds are white or pale blue or green in fresh exposures, turning to a cream color and then yellow, red, or brown as the exposure is weathered further.[5] As a swelling clay... [wikipedia]