Understanding Yellow Diamonds

Perhaps the most fantastic of yellow gems, yellow diamonds are gaining popularity. These gems range from muted brownish hues to vivid yellows with hints of orange or green, and combine beautiful color with the durability and brilliance of diamond. Yellow hues aren't as uncommon as other diamond colors, but can reach higher levels of saturation than most fancy colored diamonds. The high demand for these gems keeps prices comparable to white diamonds. However, the four Cs of fancy colored yellow diamonds vary greatly from standards for colorless or white diamonds. Before you consider buying a yellow diamond, learn about their distinct value factors.

Fancy Colored Yellow Diamond Buying and the Four Cs

The IGS colored diamond value listing has price guidelines for natural and irradiated fancy colored yellow diamonds.

Color

While cut is the most important value factor for colorless diamonds, color is the most important aspect for evaluating fancy colored diamonds. Hue, tone, and saturation are the three constituent components of color.

Secondary green or orange hues may be present in yellow diamonds, and either will raise its price. Of these, orange hues are preferable. Unfortunately, green hues occur more commonly. They can impart a murky appearance to the stone.

Yellow diamonds with low saturation will appear brown or grey. While grey gives the stone a dull look, brown can give it warmth. However, a brown secondary hue will reduce price significantly. Notably, Gemological Institute of America (GIA) reports don't mention grey as a hue. (Although people commonly refer to brown and grey as colors, the terms "brown" and "grey" reflect levels of saturation and tone).

A tone of about 20% is optimal for yellow hues, yielding a bright stone in well-saturated specimens. Darker tones tend toward brown or, occasionally, green.

What Makes Color "Fancy?"

Most consumers are more familiar with colorless diamonds and have heard of the GIA's D-Z color scale for grading diamonds. Gemologists use this scale to determine the amount of yellow tint in a colorless diamond's body color. Anything with more yellow than a "Z" is fancy.

Unlike colorless diamonds, whose body color determines grade, experts grade fancy colored diamonds face-up, evaluating the color as it appears in set jewelry. The GIA rates gems as Fancy Light, Fancy, Fancy Dark, Fancy Deep, Fancy Intense, or Fancy Vivid. These designations result from assessing both the gem's tone and saturation. The GIA's colored diamond color reference chart shows examples of diamonds that fall in each of these categories.

For yellow hues, as saturation increases in light-toned gems, the designation goes from fancy light to fancy, fancy intense, and fancy vivid. The term "canary diamonds" refers to fancy intense and fancy vivid stones. For gems with low saturation, as tone increases, a diamond will go from fancy light to fancy, and then to fancy dark. If both saturation and tone are strong, the gem is fancy deep. Note that both fancy and fancy deep designations encompass wide ranges of values of saturation and tone.

Because diamond color can vary greatly within GIA designations, make sure to examine your next purchase in both natural and artificial light. Furthermore, take care when buying from an online vendor. Not all websites have good pictures of their wares.

Cape Diamonds

Named after the Cape of Good Hope, where most diamonds exhibit a faint yellow hue, the term "Cape Diamonds" refers to "faint" or "very light" yellow diamonds. Although not fancy colored by the GIA's scale, they can be lovely - and inexpensive - alternatives to true fancy colored yellow diamonds. Due to the colorless standard for white diamonds, Cape diamonds are generally considered "off-color." However, these gems can be bright and beautiful.

Jewelry Metal Considerations

With yellow gems, the color of the metal setting can affect their appearance significantly. While yellow gold will deepen the diamond's color, white gold and platinum can make the gem appear lighter. If you plan on buying a loose gemstone, keep in mind that the setting can alter your perception of the stone. Likewise, those purchasing a yellow diamond already set in jewelry should know that a new setting could alter its appearance. If you prefer the look of white gold but the price of lighter toned gems, consider setting the diamond in yellow gold with a white gold ring to make the most of your budget.

Clarity

Fancy colored yellow diamonds are generally eye clean. Gems with eye-visible flaws (I1 grading) are available at a hefty discount. Of course, diamonds with higher clarity grades (VVS, IF, or F) will hold higher value than those with small inclusions (S). Any fancy colored diamond with low transparency won't hold high value, but some inclusions, especially in large specimens, are acceptable.

Cut

For yellow diamonds, radiant cuts may be ideal. While still brilliant, the depth of this cut can intensify diamonds with lighter colors, and bring out the best in gems with already beautiful color.

Brilliant cuts reduce the color in these gems, and are less common.  Importantly, grade reports only give a cut grade for brilliant cuts. If you're looking for a diamond with a different cut, some additional research into the proper proportions can help you assess your next gem's quality.

Carat

Yellow diamonds are more common than most fancy colored diamonds, but are still rare in larger sizes. However, diamond pricing is based on the category that the diamond's weight falls into, and prices per carat jump at these boundaries. For example, a 0.99-ct diamond will be available at a discount compared to a 1.00-ct diamond of the same quality.

Type Ia and Type Ib

You'll frequently encounter the diamond descriptor, "type." These scientific designations don't directly correspond to the gem's beauty. However, they do reflect rarity. Type I diamonds contain nitrogen, while Type II are nitrogen-free. Since nitrogen causes yellow color in diamonds, all fancy colored yellow diamonds fall into the Type I category.

Type Ia diamonds contain clusters of nitrogen within the carbon crystal structure of the diamond, while Type Ib gems have single nitrogen atoms distributed in the crystal. 98% of diamonds are Type Ia. While Type Ia diamonds can have bright colors, this occurs more typically with Type Ib. For example, canary diamonds, with exceptionally bright yellow hues, are often Type Ib. Gemological laboratories can determine diamond type using Fourier transform infrared spectrometry. However, a standard diamond grade report doesn't include diamond type.

Grade Report: Rarity or Beauty?

Fancy colored diamond grade reporting can assign the same designation to vastly different gems. Because greyish colors exhibit a deeper tone, these can have a "better" descriptor than gems without grey. While attractive gems within the same category will always have a higher price, the grading system causes price jumps for gems just over the category border. Keep in mind that these designations don't factor in all of the qualities of beauty. Rather, they more closely reflect a stone's rarity.

Color Treatment

Some treatments can improve diamond color. Gemological laboratories can reliably detect them, and treated specimens generally exhibit very vibrant hues. Gems that have undergone treatment are available at a significantly lower price than untreated natural diamonds. Gemological testing routinely includes tests for treatments. The report will note any treatments.

Coating

Some diamonds may be coated to mask an unattractive color. Coatings are susceptible to wear, and buyers should be cautious when cleaning, polishing, or resetting a coated gem.

High Pressure-High Temperature Treatment (HPHT)

Some inexpensive brown diamonds are put into a high pressure and high temperature (HPHT) environment, which alters the gem's color. While this process does increase the diamond's price, it's still heavily discounted compared to equivalent untreated yellow diamonds. This permanent treatment won't require further care.

Irradiation

Other diamonds received radiation treatments, which can produce yellow colors. These diamonds may change color with extreme heat. Owners of an irradiated diamond should always inform their jeweler whenever the setting needs repair. Even a jeweler's torch can alter the color of such gems.

Annealing

Heating and cooling diamonds in a controlled environment can also produce yellow diamonds. This process is sometimes performed after irradiation, but sometimes on its own. As with radiation treatments, annealed diamonds can change color when heated. Keep these diamonds from strong heat sources.

Synthetic Yellow Diamonds

Laboratories can synthesize yellow diamonds. Some consumers prefer synthetic gemstones for ethical reasons, and they're often available at a lower price.

Yellow Diamond Simulants

You might find nearly any yellow gem in use as a simulant for fancy colored yellow diamonds. Zircon, a natural gem with brilliant dispersion, might be the best imitation. Topazolite, the yellow variety of andradite garnet, and Mali garnets, a mix of grossular garnet and andradite chemistry, also exhibit high dispersion with bright yellow hues. Synthetic cubic zirconia is a common diamond substitute and available in yellow hues.

Other yellow gems include topaz, citrine, sapphire, and tourmaline. Yellow glass may also simulate yellow diamonds.

Addison Rice

A geologist, environmental engineer and Caltech graduate, Addison's interest in the mesmerizing and beautiful results of earth's geological processes began in her elementary school's environmental club. When she isn't writing about gems and minerals, Addison spends winters studying ancient climates in Iceland and summers hiking the Colorado Rockies.

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