Look up the word opulent and you find the descriptions of lavish, wealthy, luxurious, magnificent, and sumptuous. And at the end of this list should be the word….opal. Because opals are one of the richest looking gemstones on the market with every stone being unique, and every stone offering its own personality. But how do opals get those opulent colors? The answer is easier than one might think.

 

The science behind the opal is most likely right there on your coffee table or desk. That’s right, just look at the business side of a CD and you see the science behind the opal, the diffraction grating. You can see an example of this at right and in the image of this weeks banner at the top of this page. A diffraction grating is a series of microscopic spheres that serve the same purpose as a prism….they break the light down into its spectral colors

Let’s look at the graphic at left. Opals have a diffraction grating made of tiny spheres of silicon that all form in planes or rows throughout the stone. And since they are in all sorts of patterns and combinations, they create the wonderful play of color for which opals are famous, and they are the source of the opulent colors of opals.

 

One of the most important factors about opal color is the direction and quality of the light that interacts with the silicon diffraction grating formation.  The light must be above the stone to provide you with the true play of color in the opal. At right you can see a slide set that shows an opal lit from below and above. Notice how the opal becomes translucent and without color when lit from below. The light must be from above the stone to provide the play of color.

 

Once you have a good light source and a good viewing angle, its simply time to enjoy your opal.  At left is a slide show of an opal in 10x to 90x magnification. This demonstrates how unique the formation of the opal is, and how the colors of opals will all form a unique patter of shapes and colors.

 

And below is a look at the same location of an opal and at the same viewing angle, but using different lighting directions. Here you can see how the same area of the opal will provide a beautiful red color with the light at one angle, and then the blue and green colors in the same location but with the light moved.  This demonstrates how opals offer a wonderful array of colors that are each in unique patterns and hues.

We hope you enjoyed this look at the opulent opal colors. The study of gemology is full of beautiful and unique wonders in every gemstone you find.

 

 

Source: International School of Gemology