Fire opal is a bright orange variety of opal. It is particularly popular in jewellery because of its dramatic colour.
It can vary from completely translucent without any opalescence (vaguely speaking, a white-blue to orange-coloured ‘glow’ appearance in the stone) or iridescence (where the hue of the surface of the stone changes according to the angle from which it is viewed), to semi-translucent with highly visible flashes of iridescent colour (also known as fire).
It is primarily found in Mexico, so is often known as Mexican fire opal. Fire opal was known to the Aztecs between about 1200 to 1519 AD.