CRYSTALLITE, a name given by Vogelsang to the micro scopic bodies occurring in many glassy igneous rocks, such as obsidian, pitchstone and tachylyte. Though possessing no distinct reaction on polarized light and often no recognizable crystallo graphic form, they are to be regarded as incipient crystals. The larger bodies, often with good crystal form and evident double refraction, are termed microlites. According to their shape and structural arrangement crystallites are subdivided into globulites (small globules), margarites (coalescing globules arranged in rows), cumulites (cloudy aggregate of globules), and globo spherites (groups of globulites with a radiate arrangement). Other crystallites assume thread-like forms (trichites) or appear as elongated cylinders or rods (longulites, belonites, baculites). When sufficiently large to be recognizable as mineral species (microlites) they can usually be referred to felspar, pyroxene, amphibole or iron oxides. Acicular microlites bearing divergent arborescent branches are termed scopulites. The pitchstones of Arran are well known for the variety and beauty of their crystallite and microlite constituents (amphibole). In the basaltic glasses of Hawaii similar growths are formed of pyroxene.