Andamooka - opal field in South Australia known for its matrix and quality crystal which usually sells for a premium

Body colour - the back ground colour of the stone. Refer to the colour chart page

Black opal - Natural solid stone with dark body colour which enhances the spectral opal colours.

Boulder opal - thin veins of opal on sedimentary ironstone- found in Queensland

Coober Pedy - large opal field in South Australia known for quality white opal and opal fossils

Cabochon - the shape of the dome cut stone.

Calibrated - stones cut to a standard uniform size eg 6 x 8 mm

Carat - weight of a stone displayed as ct 5 cts to a gram

Chinese hat - a rough Nobby opal from lightning ridge. It appears to be a hat but it is believed to be a fossil or gas replacement.

Crystal - used to describe a translucent opal. It is a misnomer as opal does not have a true crystal structure.

Clarity - the amount of transparency of a opal

Contraluz - clear opal showing play of colour in the stone.

Concrete - porous matrix opal from Andamooka. Hard to polish - best to use a resin.

Crazed - a network of cracks across the stone.

Doublets - a thin piece of opal glued with black backing or glue to enhance the opal colour.

Dominate colour - the most obvious colour with the strongest fire.

Directional opal - the brightness of a opal when viewed from a angle. Directional opals are best suited to pendants as they display there best fire.

EBay - large USA Company with opalauctions and stores.

Enhanced - using a photo program on the internet to make the stone appear more expensive

Fire - refers to the brightness and colour play of the opal.

Fire opal - reddish opal usually from Mexico.

Feedback - the amount of positive or negative comments left after a transaction is completed by buyer and seller.

Funstone - usually a stone with potch running through the stone. Low commercial value.

Flaw - fault or impurity in a stone. it decreases its value.

Free shape - usually the natural shape the stone is found and cut to.- less opal waste

Flash - a broad or rolling flash appears as the stone is moved

Fossil - believed to be a replacement of the fossil by opal.

Grams - used to measure the weight of rough

Handling fee - usually a fee that includes work cost and shipping fees for a item

Inlay jewellery - Cementing crystal opal in to cavities of rings or pendants with black glue or background - should be valued as a quality doublet.

Jelly opal - darkish sleepy opal with a week colour play

Koroit - opal field in Queensland known for its matrix opal and boulder opal nuts. it is close to Yowah

Lightning ridge - large opal field in New South Wales. Known for the rare black opal.

--- Matrix ---

Andamooka matrix - porous type of quartzite in which opal has formed. this can be treated to appear blacker. Red is the most sort after colour. Will the lower grades can be cheap the better quality sells for high prices.

Matrix boulder- means the opal is surrounded by ironstone. Found in Yowah- Koroit and opalton

Lightning ridge matrix - usually refers to mixed and unstable material found with the opal. opal cutters will rub this away form the stone to expose healthy potch.

Mintabie - field in South Australia. Black opal of high quality has been found there.

Mine run- this is lower grade rough that has untouched and worked opal. popular with lapidary clubs as you may still find a good stone in it.

Money back guarantee - check to see if it includes a refund of the shipping and handling fee to you. you are usually expected to return it at your expense. always return it by registered mail.

Mosaic - small pieces of opal glued together to create a picture with a dome on top. Some are works of art and sell for large sums.

Muggie - a stone of lower grade value with many faults.

Night stone - a stone which shows colour in low light. Usually of high quality.

Nobby - refers to a piece of rough from lightning ridge which can appear like a golf ball or Chinese hat. some of the best quality black opal comes from Nobby material as it is very black and can have a high dome.

No reserve auction - listed as starting at 1$nr or the seller starts it at a low price with no reserve.

Nut – an opalholic or it can be an opal kernel in a ironstone congregation. Found at Yowah and Koroit opal fields

PayPal - company owned by eBay. Buyers and sellers register card and bank details for quick and safe transactions

Picture stone - a stone with potch and colour in the face of the stone in which you can usually make a picture. those stones with strong fire command high prices.

Pairs - usually a pair of similar opal sells for 30 –50 % more per carat as they are rare to find and match.

Rough opal - this can include raw untouched opal or rough slightly rubbed to expose some colour

Rub - refers to a piece of rough that has been rubbed down to expose the colour bar and is pre shaped ready for polishing

Seam opal - opal found in bars or slabs. Usually the colour bars are thin so it is hard to have a high dome

Semi black opal - opal which doesn’t have a dark enough base to be called black. Lower value than black sun flash. Usually a dark based opal that has a flash of colour when viewed from a certain angle in sunlight.

Square trade - USA Company for settling disputes between buyers and sellers. Verify sellers

Synthetic opal - laboratory grown opal. Low value - novelty value

Triplet - thin vain of opal with glass or quartz tops cemented on with a false base.

White cliffs - old opal field in New South Wales. Known for its quality crystal and opal fossils. Opal from this field usually sells for a premium

Yowah - opal field in Queensland known for its matrix opal and boulder opal nuts. it is close to Koroit.

Vertical opal - opal formed in the vertical position rather than the normal horizontal. The colour bars usually run up the stone which is the opposite to most opal. High novelty value