This clay mineral, a complex silicate of magnesium, occurs in solid and other forms including fine particles and fibers. It is found in naturally occurring sedimentary sources. It is formed as lightweight, porous clay having a big clear-cut surface area. Its chemical composition is magnesium silicate, which is hydrous in nature, and has individual particles of needle-like structure. High porosity and surface area impart this clay an excellent capacity for absorbing liquids. Granules of Sepiolite do not get disintegrated even on getting saturated with fluids.
Mg4Si6O15 (OH) 2·6H2O
Derivation of Name
It is so named due its apparent similarity to the spongy bones of cuttlefish, called ‘Sepion’ in Greek. Additionally, it can float on water due its porous nature and low specific gravity, promting Germans to name it as meerschaum ("sea foam").
Different from other clays, Sepiolite is not an encrusted phyllosilicate. Its structure can be best displayed as a quincunx, a geometric pattern consisting of five points arranged in a cross, with four of them forming a square or rectangle and a fifth in its center, of talc-tip sheets alienated by analogous channels. The chainlike arrangement creates needle like particles, rather than a plate like particles which are often produced by other clays.
Infrequently, Sepiolite is employed as a gemstone.
Sepiolite is not a very common clay due its unusual characteristics and scant occurrence. Very limited deposits are known the world over, with most of this clay getting produced from deposits of sedimentary rocks found close to Madrid, Spain.
Sepiolite is found as a secondary mineral coupled with serpentine. Its precipitates can also be found in scorched environments. It can be connected with opal and dolomite. Due to the fibrous nature of this mineral, Sepiolite layers may include the harmful material, asbestos. Even if there were no asbestos present, Sepiolite is frequently mistaken for that. For distinguishing the two, precautious diagnostic techniques are needed.
It comes in white, grayish white, white having a reddish or yellowish tinge or bluish green tinge.
Mohs scale hardness