- A brown to colorless mineral, ZrSiO<sub>4</sub>, which is heated, cut, and polished to form a brilliant blue-white gem.
- A mineral occurring in tetragonal crystals of adamantine luster and yellowish to brownish or reddish color: its hardness is somewhat greater than that of quartz.
- A mineral consisting predominantly of zirconium silicate (Zr2SiO4) occurring in tetragonal crystals, usually of a brown or gray color. It consists of silica and zirconia. A red variety, used as a gem, is called <stype>hyacinth</stype>. Colorless, pale-yellow or smoky-brown varieties from Ceylon are called <stype>jargon</stype>.
- an imitation gemstone made of cubic zirconia.
- a coarse-grained syenite containing zircon crystals and often also elæolite. It is largely developed in Southern Norway.
- A mineral occurring in <xref>tetragonal</xref> crystals, usually of a brown or grey colour and consisting of <xref>silica</xref> and <xref>zirconia</xref>.
- A crystal of zircon, sometimes used as a false gemstone.
- a common mineral occurring in small crystals; chief source of zirconium; used as a refractory when opaque and as a gem when transparent