spongiolite

from The Century Dictionary.

• noun A fossil sponge-spicule; one of the minute silicious elements of a sponge in a fossil state.

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

• noun (Paleon.) One of the microscopic siliceous spicules which occur abundantly in the texture of sponges, and are sometimes found fossil, as in flints.

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

• noun paleontology One of the microsporic siliceous spicules which occur abundantly in the texture of sponges, and are sometimes found fossilized, as in flints.