Phacolite

Part of speech: noun

Definitions

1. A hydrated aluminum silicate mineral of the zeolite group, usually found as lens-shaped crystals in volcanic rock cavities
2. A zeolite mineral made of hydrated calcium aluminum silicate that typically forms lens-shaped twinned crystals in basalt
3. A member of the zeolite family of minerals, a porous hydrated silicate that often occurs as small lens-shaped crystals

Etymology: Phacolite is a technical coinage, built from the Greek "phakós", meaning "lens" (from the lentil plant, whose seed is lens-shaped), plus the combining element "-lite", from Greek "lithos", "stone". The name describes the mineral's habit: it forms flattened, lens-shaped crystals, which is why mineralogists chose a word for a lentil to name it. The word belongs to the zeolite group, a family of hydrated aluminosilicate minerals whose members were named by their shapes or chemistry. Its name follows the same pattern as many other mineral names coined from Greek roots, so a reader who knows "-lite" from words like "megalith" or "monolith" can read the word at a glance.