CRYSTALLITE
crystallite
(noun) any of numerous minute rudimentary crystalline bodies of unknown composition found in glassy igneous rock
Source: WordNet® 3.1
Etymology
Noun
crystallite (plural crystallites)
A small region of a solid that consists of a single crystal; a grain.
Source: Wiktionary
Crys"tal*lite (krs"tal-lt), n. Etym: [See Crystal.] (Min.)
Definition: A minute mineral form like those common in glassy volcanic
rocks and some slags, not having a definite crystalline outline and
not referable to any mineral species, but marking the first step in
the crystallization process. According to their form crystallites are
called trichites, belonites, globulites, etc.
Source: Webster’s Unabridged Dictionary 1913 Edition