Opals make for beautiful precious stones. As the October birthstone, opal gemstones make an excellent birthday gift and a very romantic anniversary present. Before you invest in an opal for your collection, be sure that you’re getting a real opal. High quality, real opals have several telling characteristics that you can use to ensure that you get the best gemstones for your budget.
Check for uniqueness
There are no two opals that are exactly alike. If there are two opals on display that appear to be exactly the same, you may be looking at a synthetic or plastic stone.
Watch for the rainbow
The more of the stone that is coloured, the more valuable it is, regardless of type of opal. Opal gemstones spectacularly display all the colours of the rainbow so as you look into the stone, watch for strokes of rainbow colours! Be sure to look closely at the pattern. Opals created in a laboratory often display bright colours in large patches of colour. The pattern is often ‘too perfect’ and ordered, and can also often display a ‘snakeskin’ pattern.
What is the body tone?
If the stone has a white body tone or is transparent, the opal is very likely to be a genuine gemstone. All synthetic opal stones are dark in body tone because they have a black artificial backing.
Look at the side of the opal
If the side of the opal has distinct visible ‘layers’, it may not be a solid stone. In this case, one of the layers will be a thin slice of opal, attached to the dark backing. Some synthetic opals will have a third clear layer, which is domed on top of the opal.
Turn it over- what’s on the back?
Check out the back of the opal. If it feels or looks like a hard dark plastic, it’s probably a synthetic stone. Look at the side of the stone again and see if the ‘join’ between the opal and the backing is perfectly flat (i.e. the line around the circumference is perfectly straight). Most genuine solid opals have an irregularity in this area – curved or bumpy due to their natural formation – whereas a man-made stone will be perfectly flat.
Glassy or cloudy is a no go
If the surface of the opal is glassy and you can see through the top layer from the side view, the opal may be synthetic. Natural opal is not typically glassy on the top. If the opal is cloudy or becomes cloudy after a while, it is probably synthetic. The cloudiness happens when stone has been worn in water over a long period of time and the water has caused damage between the glue layers.