The Collaborative International Dictionary
Smectite
Smectite \Smec"tite\, n. [G. smectit, fr. Gr. ????? a kind of fuller's earth, fr. ????? to wipe off.] (Min.) A hydrous silicate of alumina, of a greenish color, which, in certain states of humidity, appears transparent and almost gelatinous.
Wiktionary
smectite
n. (context mineralogy English) Any of many clay phyllosilicate minerals that have a relatively open structure
Usage examples of "smectite".
Martian smectites were aluminosilicates, she found, meaning each unit of the clay had a sheet of aluminum octahedrals sandwiched between two sheets of silicon tetrahedrals.