Australian Opal Identification

Play of Color

• Opals display a "play of color" unique among gemstones, says OpalInformation.com. A gem may feature one, several, or all of the colors of the spectrum. Although this coloration was long thought to be caused by iridescence, it is now known to be the result of diffraction.

Light Opal

• The body tone of light or crystal opal is milky white or translucent. This is the most commonly found opal in Australia.

Black Opal

• The body tone of black opal is blueish-black to dark gray. Its rarity makes it more expensive.

Boulder Opal

• Less valuable boulder opal forms on an ironstone backing and may be light or dark.

Other Opals

• Man-made opal stones can be created by gluing a slice of opal onto a black background, but they lack durability. Synthetic opals are now available, but their very regular play of color and lack of inclusions are tip-offs that they are not the real thing. Sandstone opal may be treated to resemble black opal but can be detected by its porosity and lower hardness and density.