microlith

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A very small blade made of flaked stone and used as a tool, especially in the European Mesolithic Period.

from The Century Dictionary.

• noun A name proposed by Vogelsang, in 1867, to designate the “microscopic acicular components of rocks”; a “microscopic individual” (Zirkel).

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

• noun (Min.) Same as microlite, 2.

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

• noun archaeology A small stone tool.