DICTIONARY

Andamooka Mining Area in South Australia. Producing Crystal Opal and treating matrix opal

Assembled Opal Opal that has been glued together

Boulder Opal Formed in cavities and cracks of ironstone, usually from Queensland, Australia

Black Opal Naturally occurring solid opal with a coloured face and black backing

Black Crystal Opal Solid opal which is transparant to translucent opal. Viewed from the top, it compares at least with N3 in darkness rating

Blue Opal Solid opal with a blue base color

Cabochon The rounded surface of a cut stone

Calibrated Opals cut to standard dimensions

Carat Standard to express the weight of gemstones. One carat equals 0.2 grams

Chinese writing Type of opal pattern with criss crossed strokes of colour looking like oriental letters

Clarity The degree of transparancy of an opal

Clarity Cross A black cross on a white background to measure the degree of clarity of an opal

Common Opal Opal which does not show any play of color. Potch is another name for common opal

Cracked Opal Opal with one or more breaks in the opal

Crazed Opal Opal with a multitude of little cracks

Crystal Opal Transparent/translucent opal

Directionality Degree of which an opal's colorplay is showing when viewed from various angles

Dome The arch of the top of an opal. Rated as high, medium and flat dome

Doublet Opal with an attached dark coloured backing

Free-form A naturally shaped opal - something other than an oval or round shape

Harlequin A regular mosaic-like chromatic pattern in rounded, angular, or roughly square patches of equal size

Inclusions Non-Opal or Common Opal showing in the face of the opal

Jelly A type of opal with indistinct, fuzzy colours

Lightning Ridge Mining town in New South Wales. Famous for its black opal

Matrix Any material with specks or little seams of opal running through it

Multicolor Opal which has at least three distinct fire colors

Night Stone Opal which shows very bright colors in low light

Nobby Nodule of opal almost exclusively from Lightning Ridge

Parcel A collection of any number of opals, either rough, rubs or cut, offered for sale

Picture Stone Opal which shows an images. This might be created by the precious opal or in combination with colors of the motherstone

Pinfire Type of opal pattern where specks of different colours cover the whole stone

Potch Opal without any colour, also called common opal

Ribbon Type of opal pattern with the colour running in stripes

Rough Opal Opal in its natural state; as it comes out of the ground

Rubs Opal pieces initially shaped with waste material/sand removed but not yet cut and polished

Seam Opal Opal found in a layer rather than in nobbies

Solid Opal A naturally occurring solid piece of opal, cut into a stone

Sunflash Opal showing colour only from certain angles when exposed in light

Synthetic Opal grown in a laboratory. Present day manufacturers of synthetic opals include Pierre Gilson (the original manufacturer), Inamori (a Japanese manufacturer) and unspecified Russian and Chinese manufacturers

Triplet A stone comprising of a thin layer of natural opal with an attached dark backing and a clear capping

Yowah Nut Small ironstone boulder, containing opal either as a solid kernel or in concentric layers