a complex hydrous silicate of aluminum and magnesium, a light-colored, soft clay mineral, often found in veins and cavities in serpentine and basaltic rocks
Origin:
Swed saponit < L sapo: see saponify & -ite
See saponite in American Heritage Dictionary 4
noun
A clay mineral that is a hydrous silicate of aluminum and magnesium and occurs in soft amorphous masses in the cavities of certain rocks.