?7 2 CLAY GENUS. SIXTH species.- .&t m ' . n . Tjr Bunitein.—vlerner. . . -r ’ Pumice. -iseo *!H: ' O.:;: • , bhiS- ‘ 1 ■ . -}ii. External Characters. Its colour is light yellowifh grey, and fmoke grey » fometimes verging on dark greyifh white, and light : afh grey. It is fmall and lengthened veficular. '* The Iuflre of its principal fra&ure is gliftenmg* paffing to Ihining, and is pearly ; the crofs fracture i* fbining and vitreous. Its principal fradture is parallely curved fibrous, the crofs fradture uneven and imperfedtly conchoi- dal. , Fragments indeterminately angular, blunt edge and fplintery. Generally tranflucent on the edges. Soft and very foft, fometimes approaching to hard. Completely brittle. Pretty eafiiy frangible, Is clm ud