Opal

Above A beautiful play of colours show in this opal doublet - and it looks better in real life, as the effects change when the stone is moved.  The centre of the stone is rather dull.  And that’s why it’s never been mounted in jewellery.  Click here for larger image, opens in a new tab.
Below Older type ofsynthetic opal from a scrap ring; good play of colour, but the sharply defined areas of colour (chicken-wire effect) reveal it as synthetic.  Modern synthetics are much harder to identify.
This stone is soft and some scratches and damage are visible, especially in the larger image. Click here for larger image, opens in a new tab..

The pictures do not reveal the way the coloured zones are actually inside, not on the surface, of the gem,  Just visible when you turn the stone, and amazing through our microscope

A hornblende rod with accretions is embedded in this fire opal.  The light coloured area to the left is a reflection from another facet.  Click here for larger image, opens in a new tab.

Opal consists of minute spheres of silica, separated by air and water.  Normally the spheres are of random size, and the stone is translucent, and not of any use in jewellery - it’s called common opal.  But light is split as by a prism on passing through the spheres, so if the spheres are all the same size, the light is seen as brilliant flashes of colour (fire), the exact shade depending on your viewing angle and the size of the spheres.  Breaks in the array of spheres cause the hard edges between different areas of colour.

It’s a Lucky Stone

In Classical times the opal was highly regarded.  Mark Anthony outlawed a senator who refused to yield his opal!  The stone was believed to bring good fortune, and warn of poison.  Along with many other stones, it was considered a protection against disease

Is it an unlucky stone?

In 1829 Sir Walter Scott published Anne of Gerstein.  One of the characters wore an opal which changed colour according to her mood.  Holy Water was sprinkled on the stone, and she fainted and then died.  Sales of opal collapsed. But not for long.  Queen Victoria loved the stone, and its popularity was restored.
Another suggestion, in the past opals often shattered.  Plague victims were found wearing shattered opals; an unfortunate but logical connection was made!  Again there is no need to worry about this legend.  Modern opals seldom shatter.  The issue is better understood, and stones are carefully treated to avoid the problem.  Also most are sourced from Australia, where the stones are much less prone to breaking up.

Treatments before Purchase

Opal can be impregnated with oil, wax or resin to conceal flaws and enhance the colours.  Resin is permanent but oil or wax will be lost with time.  So buy from a reputable source.

Lab grown opals

Our picture shows an older type, which is easy to spot.  Modern synthetics are much harder to identify, and very cheap to make, so we encourage you to buy from reputable shops.
The colours of synthetic opal are superb, but most prefer natural stones.

Doublets and Triplets

Precious opal is valuable, and the better the fire the greater the cost.  To make it more affordable, some of the very best is thinly sliced, and cemented to a cheap backing (often black onyx).  Black glue is often used, as that enhances the colours.
Triplets use even less opal, as a very thin layer of opal is protected by a top covering of glass or quartz.
Plastic can be used as the top layer.  This is too soft, and soon scratches, spoiling the appearance of the opal.  That was why we suspected a gem we examined was plastic.
These stones give a beautiful effect at an affordable price, so are worth considering.  However they do require extra care, as water can seep between the layers.  You must choose between a longer-lasting real opal, or accept the disadvantages of a doublet in return for greater beauty at the same price.

Fire Opal

It’s common opal stained by iron oxide, which gives it a beautiful colour.  The stone. being composed of tiny spheres - like all opal - is translucent.  On rare occasions, when the spheres are the right size and alignment, flashes of colour are visible, as in precious opal.

Caring for Opal

Along with many other semi-precious stones, opals can be scratched if worn (especially in rings) when doing rough work - and a badly scratched opal will lose much of its beauty.  So never wear them when working.  Keep them for fun times.  The stones are slightly porous, so should not be soaked in anything.
Badly scratched opals can be re-polished, but there is always a small risk they will shatter while being polished.  Consult your jeweller for further information.