Definition of elvan in English:

elvan

Pronunciation /ˈelvən/ /ˈɛlvən/

noun

Geology
  • Hard intrusive igneous rock found in Cornwall, England, typically quartz porphyry.

    ‘Less frequently elvan has been met with in apparently isolated masses.’
    • ‘Molybdenite and corundum are also found in the schist through which the elvan dykes have cut.’

Origin

Early 18th century perhaps via Cornish from Welsh elfen ‘element’.