Could you believe that until 1960 or so no one actually knew how opal got its color? Firstly, let’s answer the question what color are they? The answer is simple: every color you could think of. Opals cover the full spectrum of color.
Then there is just about every mix of colors that you might imagine. I don’t think I could name a color that I haven’t seen in opal.
It is easy to understand why some gems get their color. Sometimes it is a make up of the crystalline structure, pearl necklace or it might be and mostly is because there is some element such as iron, copper, aluminum or something else which is basically an impurity which gives the gemstone its color. Why are rubies red? Why are emeralds green? Well, as one example, it is chromium, vanadium or iron elements in the stone which make that lovely green colour. Why are diamonds clear?
Most miners used to think and many still think that the colour of opal comes from impurities in the silica gel. Colored elements that seeped through the rock, got caught up in the opal gel and as it hardened became responsible for its color. This is just not so.
Opal color comes from its unusual structure and how white light is affected by it to break into its spectral colors. In the 1960s Australian scientists, using technology not previously available, firecracker freshwater pearl discovered that opal is composed of submicroscopic spheres which are responsible for the magic play of color. Because of this arrangement of spheres opal is the only gemstone with the natural ability to diffract light.
Naturally, the base color whether it is white, loose freshwater pearl black or non existent will play a role in what an opal looks like and the colors that we see. Even when a crystal opal is set on a gold or silver plate in a pendant it will show some of the metal’s color so there are a lot of factors which promote different colors after the stone has been taken out of the ground.
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