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Sheepyards Opal Fields


There are many factors used to value an opal. The main factors are:

Body tone: The body tone is the colour of the background of the opal if the gem colours were ignored. The body tones can vary widely. It can be black, dark (semi-black) or light opal. N1 is jet black through to N9 which is white. Below is a chart showing the different tones used.










����������Black opal���������������Semi-Black Opal���������Light Opal

Black Opal - is the family of opal which shows a play-of-colour within or on a black body tone by reference to the AGIA (Australian Gem Industry Association) Body Tone Chart N1, N2, N3 and N4 when viewed face up.

Semi Black�Opal � Also known as semi-black, is the family of opal which shows a play-of-colour within or on a dark body tone by reference to the AGIA Body Tone Chart N5, N6 when viewed face up.

Light Opal - is the family of opal which shows a play-of-colour within or on a light body tone by reference to the AGIA Body Tone chart N7, N8 or N9 when viewed face up. The N9 category is referred to as white opal. Opal with a distinct coloured body (such as yellow, orange, red or brown) should be classified as black, dark or light opal by reference to the AGIA Body Tone Chart with a notation stating its colour hue.

Colour: The most sought after colour in opal is red. The stronger, brighter and overall, the more intense the red, the better. Orange, yellow, green and blue rate in order from orange to blue, however it really depends on a lot more factors than just the colours. How much of each colour, how strong and rich the colour is, as well as many other considerations. Combinations of red and blue, red and green, turquoise shades, golden colours and electric blues are also highly valued.

Brilliance: The brilliance of the opal is one of the most important contributors to the valuation of an opal, and also the most difficulty to class. On the internet there is a tendency by some sellers to exaggerate the brightness of�an opal, especially when competing between dealers. We�refuse�to�partake in this practice! Often the use of brightness is overdone, with some dealers using 4.7 and up most of the time.

Lets look at some mathmatical facts, Mother Nature does not produce opals with brightness of 4.5+ that often.�I would say that Less than�5% of all opal that is cut, would have a�brilliance of 4.5.�Less than 1% would have a�brilliance of 5. It amazes me that 95% of the 4.5+ brilliance opals seems to be here on the internet? Are we�saying that other dealers are rip offs? Certainly not! The vast majority of opal sold on the internet, is sold at well below it's equivelent retail value regardless of what brilliance the seller states it is.�

What we are trying to say is; if you think that 2.5ct nice floral harlequin opal that you are buying for US$150,�truely has a brilliance of 5 on the 1 to 5 scale. Even though the seller clearly states it in his description, think again! Did you pay too much for it?�Probably not.

Another rule of thumb: If something looks to good to be true, it usually is!!

The brilliance scale below is the scale of brightness used to show the brightness of an opal:

Brilliance scale:






Somewhat bright




�Quite bright


Very bright


Extremely bright



The correct way to properly asertain the brilliance of an opal is to have yourself and the opal in direct sunlight with the light coming from behind and hitting the opal from over your shoulder. In other words the viewer should be between the opal and the sun. If this is not practical�the alternative and accepted practice is to use a consistent light source. Say�a lamp with a�40 W globe. The opal is then held at a distance of 30 to 40 cm from the lamp over a neutral background. it is then categorized into one of the above categories of brightness.

One important factor about opal brilliance that must be stated. As mentioned prevously, opals are valued in full direct light. Beause opals show their colour not by pigment, but by refracted light they do need light to work. Usually the better the quality opal the better it will perform in lower and indirect light situations. Unfortunatly an $80 opal is not going to display as vividly indoors as a $800 opal and in some cases will "grey out" and�of course a�$8000 opal will be even better again. There are exceptions to this, but $ for $ you will get better perfomance out of a higher quality opal.

Pattern: There are many patterns that opals show. This is not to say that they are easy to come across. Harlequin patterns would have to be the most prized of all patterns; the definition of a Harlequin opal is that it shows as square, angular colour patches set�closely together to resemble a mosaic like chromatic pattern. There is a vast array of Harlequin patterns, Asteria Harlequin, Chequeboard Harlequin, Cloverleaf Harlequin, Fishscale Harlequin, Flag and Flagstone harlequin, Floral Harlequin, Hexagonal Harlequin, Palette Harlequin, Square Harlequin as well as colour harlequins i.e. Blue and Green Harlequins.

Weight: Opal is weight per carat (ct) with 1 carat equal to�0.2 grams. Larger stones are priced higher per carat than smaller ones because of their comparative rarity. Opals being between 1 carat and 20 carats are priced high as they are the most desirable size.

Other vital points are: How an opal performs in all lights and whether the opal has a high, medium or low dome. The conclusion is that the overall beauty of the opal is the key to the pricing. Experience, how the market is performing and a touch of common sense play a large role in the valuation.

Doublets and Triplets: You should be able to pick up a doublet or triplet opal for between 1/10th to 1/20th the price of the equivilent�solid opal. Remember these are manufactured opals and usually have little or no investment value. But there are exceptions. Mounted well, in a bezel setting it would be hard to tell the difference between a quality doublet opal and a solid opal.


Don�t get too hung up in the technical jargon.

Opals hold a rare and unique beauty. If you find an opal that appeals to you, then that is "the one� for you. At the end of the day, it all comes down to personal taste and each person will appreciate different types and colours of opal in a different way.

That�s why Mother Nature made so many gorgeous opals to choose from!!