zircon

1. (uncountable) A mineral occurring in tetragonal crystals, usually of a brown or grey colour and consisting of silica and zirconia.Examples: "[…] salamanders, mermaids, chimaeras, wild men o’ the woods, leviathans, all hewn from faultless gems, thrice the bulk of a big man’s body, velvet-dark sapphires, chrysolite, beryl, amethyst, and the yellow zircon that is like transparent gold."; "Although there are dozens of different types of gems, among the best known and most important are […]. (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)"uncountable

2. (countable) A crystal of zircon, sometimes used as a false gemstone.Examples: "A zircon princess, seemed to lost her senses"countable