Vitrinite

Part of speech: noun

Definitions

1. A glossy, homogeneous component of coal formed from the woody tissues of ancient plants, used to measure the maturity of coal
2. The bright, banded constituent of coal that originates from plant cell walls and indicates how far the coal has been heated and altered
3. A type of coal particle, derived from the lignin of prehistoric trees, whose reflectance is studied to determine coal rank

Etymology: Vitrinite is a coal-science coinage, not an ancient or folk word. It was introduced in the early twentieth century by the German petrologist Marie Stopes's contemporaries in the coal-microscopy field, and its name comes from Latin "vitrum," meaning glass, a nod to the glassy, lustrous look of the material under light. The "-ite" ending is the standard mineralogical and petrological suffix used for named rock and mineral constituents, so the word is simply a technical label built from a classical root and a scientific suffix. The sense it names is more surprising than its Latin dress suggests. Vitrinite is derived from the woody tissues of ancient plants, mostly cell walls and the lignin they contained, which were compressed and chemically transformed over millions of years in peat and then coal beds. Because the glassy appearance deepens and changes as coal matures, microscopists reflectance-measure vitrinite to estimate how hot the coal has become, which in turn helps geologists judge burial depth and whether oil or gas may have formed nearby.