the world > the earth > minerals > types of mineral > hydrocarbon minerals > [noun] > coal > lignite > jet (6)
A hard black semi-precious form of lignite, able to receive a brilliant polish and used ornamentally, esp. in Victorian mourning jewellery…
= jet, n.2 1a. Obsolete. rare.
The mineral jet (jet, n.2 1a). Obsolete.
(a) = jet, n.2 1a; †(b) = ambergris, n. (obsolete); (c) a dark-coloured amber.