In the world of colored gemstones, brilliance is a good thing. So is fire. But they are actually not the same thing, and if you want to be a gems expert, it's worth knowing the difference.
In our everyday language, both fire and brilliance suggest terms like "shiny", "sparkly", "bright", "glittering" and "lustrous." But in the gem trade brilliance and fire are technical terms with specific meanings.
The term brilliance refers to the light that is reflected from the interior of a gem, not from its surface. For a colored gem such as blue sapphire or ruby, the light reflected back to the eye is colored, not white. In a well cut gem, most or all of the light that enters the stone will be reflected by the pavilion facets and returned to the eye through the crown of the stone.
A colored gem with good brilliance will be literally bursting with color from all angles. A poorly cut gem will have areas of reduced color and will thus lack brilliance.
The term fire refers to the ability of a gem to split light into the colors of the spectrum. The technical term used in gemology for fire is dispersion. The phenomenon of dispersion occurs when different frequencies of light are refracted to a different degree by the refracting medium. The gemstone most famous for its dispersion is diamond, but several colored gems are noted for their impressive dispersion, including sphene, demantoid garnet, sphalerite and zircon.
Gemologists measure dispersion with a refractrometer, and the dispersion rating is usually a number that represents the difference between the violet and red refractive indices.
But one shouldn't rely entirely on the numerical dispersion rating for predicting how much fire a given gem will exhbibit. Darker gems tend to exhibit less fire than stones of a lighter color, and cleaner stones exhibit more fire than included ones. A deeper toned gem like Tanzanite can still be very flashy, but it will typically flash just a few colors compared to the full spectrum you will see in a fine Sphene or Sphalerite.
Notable Gems from the AJS Collection
This month we feature some very fiery gems from our collection, from Sphalerite to Sphene to Zircon, Spessarite and Tanzanite. Click on any gem for details.
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An outstanding large Sphalerite from the Aliva mine in northern Spain. This gorgeous round gem is amazingly bright and fiery, with flashes of orange, yellow and green as it is turned in the light. Beautifully cut and very clean, this is a superb gem Sphalerite for your collection. Guaranteed natural and untreated.
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A deep green Sphene from Madagascar with outstanding fire. Very clean and beautifully cut, this fine gem has both amazing brilliance and fire, characteristics that make Sphene so popular with collectors. Guaranteed natural and untreated.
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A superb Honey Zircon from Cambodia, amazingly bright and fiery. This is beautifully clean material that has been expertly cut to maximize its brilliance and fire. This is an outstanding gem for the zircon collector and will make a fabulous piece of jewelry. Guaranteed natural. |
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4.56 ct Blue Zircon from Cambodia [SOLD]
A gorgeous 4.56 ct Blue Zircon from Cambodia with wonderful color saturation. This fine gem Zircon is a rich medium blue, yet with excellent fire across the full face of the gem. Very clean and well cut, guaranteed natural. |
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A fiery gem Spessartite Garnet from Nigeria with a beautiful intense orange color. This is an exceptionally bright gem that shows bright yellow and orange flashes when turned in the light. This is a fine collector's gem that will sparkle in any setting. Guaranteed natural and untreated. |
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A very fine Royal Blue Tanzanite in a perfect ring size! This is the top color in Tanzanite, with amazing brilliance and excellent fire with blue and violet flashes. Guaranteed natural |
News from AJS and the Gems World
25% off on all the Gems in our Collection !
As a way of saying Thank You to all our loyal customers, we are offering a 25% discount on all the gems in collection for the month of April.
Use this discount code at checkout: YOUR25
Important Shipping Notice
Due to postal disruptions during the Covid-19 pandemic, we are now shipping orders only by UPS Express, with delivery in 3-4 business days. Though there are occasional delays, UPS is providing excellent service and they have been successful in delivering order to most places in the world.
Please check our home page for any updated information.
Ask the Gem Experts
Each month we answer questions from our customers. We welcome your questions and you can submit a question from our contact page.
Is step cut the same thing as a cushion cut? If not, can you explain the difference? MP, USA
The term cut can have different meanings in the gems world, depending on the context. Often cut refers to the faceting pattern of a gem, as in step cut, brilliant cut and portuguese cut. At other times, cut may refer to the outline shape of the gem, as in cushion cut, pear cut or marquise cut.
I have several loose sapphires which I'd like appraised and/or graded. I notice there are many grading organisations out there, from GIA to GRS to others. I want to go about getting a reliable, affordable, fair gemological grade of these stones without spending a fortune. Is there any one appraiser/organisation you trust more than others? Please advise. BJ, USA
Lab reports from the likes of GRS and GIA are identification reports, not grading reports. They will identify your stones as natural sapphire and will indicate whether and how they have been treated. But their colored stone reports, unlike diamond reports, don't say anything about quality grade. The reason is that there are no established quantifiable standards for colored stone grading as there are for diamonds. There are simply too many variables with colored gems. That's how successful gem dealers add value -- by using their experience to acquire good stones at the right price.
All the best in gems,
Ron, May & and Rung
