harmotome

from The Century Dictionary.

• noun A mineral belonging to the zeolite group, commonly occurring in cruciform twin crystals which vary in color from white to yellow, red, or brown. It is a hydrous silicate of aluminium and barium. Sometimes called cross-stone and andreolite.

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

• noun (Min.) A hydrous silicate of alumina and baryta, occurring usually in white cruciform crystals; cross-stone.

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

• noun mineralogy A rare zeolite, a hydrated barium silicate that forms vitreous white monoclinic crystals.