“For in them you shall see the living fire of ruby, the glorious purple of the amethyst, the sea green of the emerald, all glittering together in a incredible mixture of light.”
- Written by Roman Pliny in the 1st century AD
This article aims to inform our buyers on best practices when buying opals.
Base Body Tone Guide
The base body tone guide is the best kept secret for buying opals on the internet, as most internet sellers give a fairly accurate description of the stones body tone that they are selling.
The opal association is marketing a body tone guide with opal stones and doublets so all buyers and sellers can have a uniform guide to gauge opal. These will help buyers compare opals between sellers. You should always buy off a seller who guarantees his product and grading so if you disagree you can return it.
The base body tone refers to the darkness or lightness of the opal ignoring the play of colour and brightness of the stone. The base colour can only be determined by looking down on the top of the stone and ignoring the material on the back of the stone. Only those stones ranking N1 to N4 are considered black opals. The opal price is determined by body tone, brightness, colour, play of colour, size and allowing for faults and imperfections.
See an example of an opal buying guide below:
Generally we have buying guides for sale on Opal Auctions in our Opal Literature category.
Opal Photography
It must be remembered that opal reflects light and digital cameras are not built to capture the amazing patterns and colour changes in opal.
A simple experiment is to place a stone on the floor by a doorway in natural sunlight, and move the stone back inside taking several photos along the way. You will most likely find that one photo looks amazing as if it has been enhanced.
Depending on the quality of photographic equipment and lighting sources, there will always be some variation between a digital photo and viewing a stone with a naked eye.
Sellers on Opal Auctions are expected to produce consistent photos that are representative of the opal being sold. Viewing an item that has a video can be a good way to reveal the many different faces of a good quality opal, and see the movement of colour that is not necessarily visible from all angles.
The experienced buyer will know to take all information into account, including the N tone rating, brightness, shape, dimensions and of course price.
The most common complaint is for blue opals. Most cameras capture the mauve in the stone which the naked eye can’t see. So if you see a mauve stone remember it’s most likely a blue stone.
Pastel colours seem to come out true to form. With Ethiopian opal the red is easy to capture and it will not be as bright in the hand.
If a seller guarantees his stock there is no advantage in over enhancing the pictures as he would have to return too much stock.
Brightness or Fire in the Stone
The brightness of a stone is one of the most important factors in a stones beauty and value.
On the Australian opal fields you don’t hear the words” fire” used when miners talk about how bright a stone is. The term is however used a lot on the internet to describe a stone’s brightness, and to gauge opal brightness evenly over different stones.
Harlequin Patterns
Harlequin opal is the most sought after pattern in opal due to its rarity and beauty.
On the Gemological Institute of America (GIA) website, it states: “Harlequin or mosaic - broad, angular, close-set patches of color”.
Originally rounded or floral shapes were not called harlequin but this is now common practice.
On some unscrupulous internet sites many stones are listed as harlequin as the seller believes this will increase its value. Many of these stones would not be called harlequin on the opal fields, however they can still be beautiful and valuable in their own right. It is always important to buy from an opal expert.
In my 20 years experience of selling thousands of stones, I have only had three opals which I consider to contain a true harlequin pattern.
Doublet or Natural Stone?
It is difficult to determine if an opal is a doublet when it is set in jewellery. Only by removing the stone from the jewellery can you be certain.
Take a 10 powered loop or magnifying glass to the side of the stone. As glue doesn't polish you will see a gap between the crystal and backing so you know it’s a doublet.
Alternatively, if you have a digital camera you can take a photo of the side of the stone and enlarge the photo on your computer. If there has been glue used it will be easy to see.
See our article on doublets and triplets to learn more.
Inclusion or Fracture?
Some times stones have natural inclusions that look like fractures. The best way to determine if a stone is fractured is to hold the stone up to a base of a lamp shade and roll the stone in your fingers keeping the stone in the light and not the shaded area. If there is a fracture you will see the light reflect off the fracture like a chip in your windscreen.
Natural or Synthetic Stone?
Some synthetic or imitation opal can confuse customers.
Things to watch for:
- Usually they have no inclusions or potch backing behind them
- The pattern appears to be even through the stone which is rare except for top gems.
- If viewed from the side the line of colour is in the lower areas.
- Unnatural look and fire to them.
Synthetic opal are sometimes used in triplets which are much harder to spot. Generally they are very bright with a regular pattern that looks too constant to be natural. It is best to become familiar with a few man made opals (usually advertised as synthetic or man made) so it is easier to recognize them.
Andamooka Matrix
Andamooka Matrix is a natural white opal matrix found in Andamooka, South Australia. It has been treated to look like expensive black opal. The treatment is permanent but if you reshape or cut it you will have to re-treat it.
Some of this material is called concret which is more porous than the gem matrix. It is hard to get a good polish on it as it has pores. You can use a resin like liquid glass - or in Australia we use HX3 made by Shell. This is an epoxy that soaks in to the stone and gives a good polish. The colours and fire are amazing.
On the field they call this concret which is a horrible name for such a beautiful stone. Gem matrix, which you can get a natural polish on sells for $10 - 50 per carat while concret sells for $1- 2 per carat for larger stones.
Andamooka Matrix is even great just left in a glass jar as a dazzling specimen.
$1 No Reserve Sales
$1 No Reserve auctions are a great entry point for new opal buyers, as the buyer can determine the price at which the item sells. This is generally a good indicator of the value of the item.
Of course, the cost to the seller to list a $1 No Reserve item is going to be more than one dollar, once fees, buyer communication and shipping costs have been added to the price they paid for the item.
For this reason sellers have been known to list a great variety of high quality items to ensure a good selling price, and build up their loyal repeat customer base.
Rough Opal
Buying rough opal is always a bit of a gamble as you can’t really see the quality of the precious opal within.
You can lessen the risk if you buy “rubs”. Opal rubs are pieces of rough that have been rubbed down to the colour bar so you can get some idea of the stone it will cut. There is still the risk of inclusions in the stone which may make it smaller than you expect.
Most sellers on the internet wet the rubs or rough before hand to show the colours you can expect when it is polished. Always check the thickness of rubs as if it is too thin it won’t be strong enough for a ring. Any stone around 2 mm thick is too thin and may even need reinforcing in a pendant.
You shouldn’t expect to see a good stone in cheap rough as no seller would deliberately leave it there, however some beautiful stones have been found in rough that looked as if it contained nothing.
Black nobbys from Lightning Ridge are known for there surprises as even the most experienced dealers let some stones slip through in there rough grading process. Nobby rough untouched should always be viewed as a gamble.
With white opal rough it is a rule of thumb that what you paid per gram should cut that per carat as a finished stone.
Buying rough from photos is always difficult so you should check the sellers return policy. If they don’t offer one you should consider taking your business elsewhere. It is generally accepted that if you rub, snip or touch the rough it is considered sold.
Most internet sellers want your repeat business so even if you are not happy with what you have cut you can always ask for a bonus.
Trivia & Tips
- All items should be compared in the same lighting with no natural lighting to make comparisons. 100 watt globe 20 inches above stone recommended.
- Have a set of stones to compare what you are grading. Many buyers bring their own stones for comparison to the opal fields.
- If you are buying at Lightning Ridge in the motel there is strong sunlight in the morning so many sellers try to use this to their advantage.
- Buy from reputable verified sellers, not hobbyiests advertising themselves as experts - common place practice on other auction sites.
- On the opal field a clean stone with a N1 background and a brightness of 5 will sell very quickly for top money.
- Check a sellers return policy and stock guarantee. When returning stock use registered post.
- It might pay to test the waters with a seller on cheaper items if you are interested in purchasing an expensive stone.
The buyers on the internet have a big influence over the shape of the industry. If they return over enhanced stones back to sellers, they will be forcing sellers to more accurately classify their stock so all sellers are on an equal playing field, and it will be easier to compare stock between sellers.
The future is exciting for the opal industry. This beautiful stone is now available at competitive prices to buyers who would normally not have access to it.
The gemstone industry has many levels of dealers but the internet allows you to go direct to the source. New cameras will more accurately capture the true colours of opal and there will be evolving video technology that will allow you to see a stone as if it was in your hand.
With some knowledge there are bargains to be had today. Good luck with your bidding.
Paul Sedawie
President, Australian Opal Association
Last Update: 11 Feb