Adularescence

Part of speech: noun

Pronunciation: /ˌæd͡ʒ.ə.ləˈɹɛs.əns/

Definitions

1. the shifting of a luminous sheen or opalescent glow that seems to glide across the interior or surface of particular precious stones when illuminated
2. an optical property in which a soft, cloud-like luminescence or pearly sheen appears to migrate across the body of certain gems or crystals when viewed under light
3. A glowing effect resembling a floating light or mist seen within certain gemstones when light falls on them

Etymology: Adularescence names the soft, shifting sheen of light that seems to glide across the surface of certain gemstones, most famously moonstone. Its root is "adularia," a name for a translucent variety of feldspar, which in turn is linked to Adula, the Latin name of the Adula massif in the Swiss Alps, where such crystals were found. The mineral took its name from that place, so the word for the glow is, at one remove, a mountain's name. The second half of the word, "-escence," comes from Latin "-escere," a suffix meaning "becoming" or "beginning to be," which English borrowed in words such as "effervescence" and "luminescence." Attaching it to "adularia" produces a term meaning something like "the quality of becoming adularia-like," describing the play of light that makes a stone appear to glow from within.