Glossary of Terms

Whilst not all of the terms are referred to in our website, they are included to assist you gain a better understanding of Opal terminology.

BOULDER OPAL Formed in cavities and cracks of ironstone.
BLACK OPAL Naturally occurring solid opal with a colored face and black backing.
CABOCHON The rounded surface of a cut stone.
CALIBRATED Opals cut to standard dimensions.
CARAT A metric measurement for weighing gemstones.  One carat equals 0.2 grams.
CLARITY The degree of transparency of an opal.
DOME The arch of the top of an opal.  Rated as high, medium and flat dome.
DOUBLET A doublet is made by fusing a dark backing to the back of the gem opal producing a double layered gem appearance similar to black opal.
FREEFORM A naturally shaped opal.
GOUGING The method whereby a small pick is used to remove dirt in the earth surrounding the opal. 
HARLEQUIN A regular mosaic-like chromatic pattern in rounded, angular or roughly square patches of equal size.
JELLY A type of opal with indistinct, fuzzy colors.
MULTICOLOR Opal, which has at least three distinct fire colors.
NOBBY A naturally lump-shaped piece of opal. 
NOODLING The process of searching old mine dumps for opal missed by the miners.
OPAL CUTTER A skilled person who cuts and then polishes rough opal into the finished gemstone.
PINFIRE Type of opal pattern where specks of different colors cover the entire stone.
POTCH Opal that does not contain gem color or does not reflect color.  Potch is usually white or amber colored and also referred to as ‘common opal’.
ROUGH OPAL Opal in its natural state as it comes from the ground.
SEAM A horizontal layer of opal in the ground.
SOLID OPAL A naturally occurring solid piece of opal cut into stone
SPOTTERS Term used to describe the persons engaged to follow the bulldozer to search for signs of opal (trace)
SUNFLASH Opal showing color only from certain angles when exposed in light
TRACE A thin seam of opal in a level, which encourages the miner to continue to drive on that level.
TRIPLET A stone comprising of a thin slice of natural opal with an attached dark background and a clear capping.