thomsonite

from The Century Dictionary.

• noun A mineral of the zeolite family, occurring generally in masses of a radiated structure, in spherical concretions or compact. It is a hydrous silicate of aluminium, calcium, and sodium.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Min.) A zeolitic mineral, occurring generally in masses of a radiated structure. It is a hydrous silicate of aluminia, lime, and soda. Called also mesole, and comptonite.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy Another name for ozarkite, a mineral native to the United States.