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Why Do Opals Change Color?

What is the science behind opals changing color

Have you ever seen a gem quality opal? You'll know it when you see it. It looks like a piece of rainbow fell from the sky and got stuck inside a ring or necklace. Low-quality opals are extremely common, and they have their charms but if you can spring for a higher quality one? Definitely do so.

Gem quality opals are some of the most striking gems available on the market. It can flash in almost any color of the rainbow with an intensity that can surpass the fire of even the finest diamonds. Specifically what makes opal colors change? We'll cover that and so much more. All you ever wanted to know about opals is right here!

Why Do Opals Change Color? uncut stone

Chemical Composition

Opal shares its chemical composition with quartz crystal. SiO2, Silicon Dioxide. Opal also contains some amount of water. It can contain up to 20% water! This gives opal gemstones a lower hardness, and makes it quite brittle. Opal care needs to be done extremely carefully.

Don't risk the luster of your opals when they are in need of a cleaning. Simple Shine's gentle jewelry cleaning kit is specially engineered for use with softer stones like pearls and opals. If you don't need the entire kit then just snag a bottle of gentle jewelry cleaning foam. Our products will return those opals to their original sheen without damaging their gorgeous and unique array of colors.

Reason For Color Change

Some opals have internal structures that consist of silica spheres. These orbs are capable of light diffraction. This diffraction separates light into its component colors, similar to a prism. This is known as a 'play-of-color' and it's what makes the opal so desirable as a gemstone. Opal without this diffraction capability is known as 'common opal'. I've also heard it referred to as 'potch'.

The rarer for of opal the displays this vibrant play of color is known as 'precious opal'. High quality opals that are large enough to cut can produce extremely valuable gemstones. There is even a word that the opal lends its name to. What do you think of when you hear the word 'opalescence'? Opalescence means exhibiting a play of colors like that of the opal.

Why Do Opals Change Color? necklace

Mining Locations

The largest producer of opals is Australia, followed closely by Mexico and Ethiopia. Opals are found in many places around the world in less quantity. Opals are found quite commonly in South America. Brazil, Peru, Honduras, Guatemala, Nicaragua, and of course the aforementioned Mexico.

They're also found in Eastern Europe around Hungary, Slovakia, and Czech Republic. Americans might find an opal in Nevada, Idaho, Oregon, or Louisiana. Opals are much less commonly found around Asia. If you're hunting opals in Asia your best bet would be around Indonesia.

Color Shift Over Time

I mentioned a little earlier that the opal was a sensitive stone, but just how sensitive is it? Well in addition to being brittle, changes in humidity are enough to significantly change the color of your gemstone. There is almost no other stone that is so effected by its environment.

I've seen an opal change in a period of just 6 months from a cool blue to a fiery red. This might seem like a great and interesting selling point, but it doesn't come without some risk. These color changes can quite possibly remove that enjoyable play-of-color from your opal, and once that happens there is no going back.

๏ปฟ๏ปฟWhy Do Opals Change Color? geode

Assembled or Composite Opals

There are many strategies that jewelers utilize to preserve the opal's natural play of color. One of these procedures is to create an assembled or composite opal. These opals consist of multiple pieces which can add to the stability of the stone. Opal doublets are a thin layer of opal glues to a backing of host rock.

Opal triplets are possibly the most solid and stable. Opal triplets are usually made with a backing of obsidian with a thin layer of opal on following and finally a thin layer of quartz or synthetic corundum is added on top. This final layer not only protects the sensitive opal but is able to magnify its beautiful and unique bevy of color.

Synthetic Opals

Given opal's unique status, humans have engineered a few different ways to attain even more of them. Synthetic opals are lab-created but have the same chemical composition as a natural opal. While synthetic opals have the unique play of colors demonstrated by true opals, they sell for a much lower price.

Synthetic opal started being created in the 1970s, and the production has gotten to the point where it's hard to an untrained eye to tell the difference. Even trained gemologists can be fooled by synthetic stones and sometimes need to send them to a laboratory for confirmation.

Imitation Opals

Our last stop on our journey through the wide world of opals aren't opals at all. These imitation opals are usually made of glass or plastic. They are more durable and many times cheaper than true opals, but they will rarely be able to fool an experienced eye.

Imitation opal production methods are becoming more refined, and some come close to the real thing but all is revealed under a jeweler's loupe. Authenticity doesn't matter as much to some. The fact that they're more durable and much cheaper are appreciated by consumers. Imitation opals can be beautiful and legitimate products so long as they are sold with full disclosure to the customer.


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