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. |
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| 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. |
