Colors of Gemstones
“The best color in the whole world is the one that looks good on you.”
Gabrielle Bonheur ‘Coco’ Chanel (1883-1971)
It is no surprise that color is the most important factor when evaluating a gemstone. In terms of percentage, color contributes to about 50% of its final value. Weight (in carats), cut and purity directly affect the color of a gemstone.
But where beauty is concerned, the issue remains highly subjective, and ultimately depends on the observer. This does not mean that there are no criteria for judging gemstone color; on the contrary, these do exist, but should never overrule personal preference. It will surprise nobody that the more attractive a gemstone’s color, the greater its value.
Two factors determine whether a color is highly sought after: fashion and rarity. The first is easily understood - fashion determines the success of a color. If nobody finds a gemstone’s color attractive, its rarity will not have any value. In contrast, if the color is popular and the gemstone rare, such as Paraiba Tourmaline or Padpradschana Sapphire, we are looking at a gemstone superstar. In general, intense colors are preferred to dark or clear hues, but there are exceptions, such as Rose de France Amethyst, extremely popular during the Victorian period.
How a colored gemstone is described may affect whether or not a person wishes to own it: there are specific words and phrases for describing the multitude of gemstone colors, such as the noble red Spinel, cornflower blue Sapphire, or ‘AAA’ (triple A) seal indicating superior quality (color and clarity).
But what, exactly, is ‘color’?
In the most simple terms, there are two kinds of colored gems:
- With their own color (Idiochromatic): a coloring element is incorporated into the crystal structure itself, imparting the gem with a characteristic color. Peridot, for example, is high in iron, representing 12-15% of total mass, which confers the gemstone its green streaks.
- Colored by other elements (Allochromatic): in this case, the gemstone’s color is determined by small amounts of coloring elements that are not part of its normal crystalline structure, and/or by imperfections in the crystal (centers of color). In their pure state, these allochromatic minerals are colorless. Without coloring elements (and/or centers of color), all Sapphires, for example, would be colorless.
Color depends on response to light. The color of some gemstones, such as Opal, is determined by how light refracts into beams that change depending on the viewing angle (color play). However, for most gemstones, like most objects, our perception of color entails an extraordinary transformation. As revealed in a rainbow, white light is the result of single colors in the spectrum: blue, green, orange, red, violet and yellow. When white light travels through a gemstone, some of these colors are absorbed. The colors of the spectrum that are not absorbed combine to bring the gemstone’s color to life. Absorption of a few colors is called ‘selective absorption of light’ and is always the same for any individual gemstone. A gemstone that allows all colors of the spectrum to pass through is colorless; one that absorbs them all is black. A red gemstone appears so because it absorbs all other colors of the spectrum except for red. It is changes in the color spectrum of the light source which explain why gemstones look different under different lighting. Even minor variations in the light source may have a relevant impact on our perception of a gemstone’s color. In extreme cases, this may even result in a change in color. While some gemstones appear more beautiful under natural light and others under artificial (incandescent) lighting, gemstone colors should remain beautiful regardless of lighting conditions.
An 'idiochromatic' gemstone, Peridot and an 'allochromatic' gemstone, Yellow Sapphire
Color is influenced by three components:
- Hue: the position a color occupies on the chromatic scale. This is referred to as shade, tint or color sensation.
- Tone: this is the brightness or darkness of a color.
- Saturation: is the intensity (or strength or purity) of a color. Saturation, combined with transparency more than tone, typically affect the beauty of a gemstone. Although there are several different classifications for color (e.g. GemDialogue, GemEWizard and GIASquare), there is no universal standard for defining gemstone color. This is mostly due to the fact that colored gemstones are such a subjective phenomenon, and partly because sellers often created their own personal classification systems, such as triple A.
Color can be an excellent way to choose a gemstone, but remember that color alone is not a reliable means of identification. Even an expert may be fooled! Color can certainly help, but other visible indicators such as inclusions, signs of deterioration (hardness), pleochromism, fire and sparkle are also of fundamental importance. These aspects, along with the use of gemological instruments such as microscopes, enlargement and refraction loupes, are the only way to obtain certainty. Below, some popular gems are grouped by their colors - get back in black (black gems), discover heavenly blues (blue-violet gems), become a white knight (colorless/white gems), make them green with envy (green gems), multiply your choices (multicolored gems), warm your heart (red-pink gems) or simply brighten your day (yellow-chocolate gems). A question we have been asked often is: "What color gem suits every person?" While blue is one of the most popular choices, its richer tones can be too dark for some people. The color of the sky and tropical seas, medium or aqua blues suit almost any skin tone. Examples include Aquamarine, Ceylon Sapphire, Paraíba Tourmaline and Turquoise. Don't believe me? Just look at the popularity of blue jeans.
Ever synonymous with elegance and refinement, black is a non-color that is easy to wear and personifies style, power and depth. Its capacity to adapt to any color and emphasize them, in the case of primary colors, has made black a versatile and loved shade. To the Ancient Egyptians, black personified rebirth and the afterlife, while the Maasai consider it to be a symbol of life and prosperity. Black gemstones are gaining a growing foothold in the precious stone market, likely due to the popularity of the Black Diamond, a fascinating variety with a bright sheen which owes its color to minuscule inclusions of gray graphite. Onyx, which according to legend was created from one of Venus’ nails, is considered a black gemstone, although many examples display white striations. Imbued with strong symbolism, Onyx and Obsidian, a volcanic silicate, are two gemstones with a rich metaphysical tradition and long history. Black Spinel, a rare black variety belonging to the Oxide mineralogical class, is a highly sought after gemstone with noble origins, with a transparent fundamental structure and glassy brilliance. Despite its mineralogical rarity, it remains a relatively affordable gemstone to this day. In addition to these examples, one must never forget the extremely rare Black Star Sapphire, on the surface of which linear needle-shaped inclusions produce a wonderful star of light. Depending on personal taste, the stone that best suits personality and personal style may be selected.
Here are some Black Gemstones:
Other black gemstones include Black Spinel, Hematite, Obsidian and Black Tourmaline.
Blue to violet Gemstones
Blue is one of the most well-loved colors in the world, and never goes out of fashion. Known for its relaxing and metaphysical properties in chromotherapy, it has historically been associated with meditation, inner space and harmony. In literature, it recalls distance, nostalgia and purity. It is believed that people who prefer this color are serene, balanced and able to resolve their own internal conflicts. The world of precious stones has every shade of this beautiful color on offer, able to satisfy even the most demanding tastes. From the intense blue of the classic Blue Sapphire, to Turquoise, a gemstone with such a unique color that it named the color itself, a multitude of shades are at our disposal. Aquamarine, an azure blue Beryl, has the presence of trace amounts of iron to thank for its color; various concentrations of this element result in a marvelous palette ranging from pastels to the deepest of blues. Another gemstone famed for its color is the highly sought after Paraiba Tourmaline, which displays extreme sheen and is in particularly high demand. Its colors vary, geologically speaking, from greenish-blue to green azure, greenish azure, to blue and bluish-violet. Within the purple chromatic scale, Amethyst is probably the most well-known and loved precious stone, thanks to its uniform color and the extraordinary eye-clean transparency of its crystals. Within the Quartz family, the Blueberry Quartz, a relatively new and very rare stone on the market, was immediately very successful; unfortunately, the production is extremely limited due to both extractive conditions and its mineralogical scarcity, factors that have affected demand. Rarity and beauty are the common denominators for Tanzanite, considered the most important gemological discovery in recent years, particularly its inimitable intense veiled blue tint.
The table below displays a few of the most well-known blue to violet gemstones:
Other blue-violet gems include Ambligonite, Azurite-Malachite, Blue Opal, Sodalite and Sugilite.
According to tradition, the color green symbolizes superior knowledge and balance, and exudes a sense of justice, compassion and harmony. A sign of a strong personality, this color represents immortality and fertility, and the power of nature. There are many gemstones that present this color, from the grass green shades of Peridot to the intense greens of Emerald, particularly loved by Cleopatra, and already then a stone symbolizing power. Russian Diopside, drawing its color from chrome like the more famous Emerald, owes its popularity to the rich color, which is occasionally flecked by shades of blue. Another particularly desirable and very rare gemstone is Russian Demantoid, the stone favored by famed Jeweler Fabergé for its brilliant greens, married to a sparkle worthy of a Diamond. The various colors of Jade include marvelous examples of green, both transparent and opaque, owing their shades to the presence of chrome. In addition to the Empress of Chinese Jewelry, with its long and rich history, another gemstone merits a mention for its color - Tsavorite. A recently discovered gemstone (1961), Tsavorite is a Green Grossularite Garnet. Colored by vanadium and with a particularly lively sheen, Tsavorite has a high refractive index, double fire and monorefraction, factors that serve to further accentuate its marvelous green.
Some of the most well-known examples of green gemstones are presented below:
Other green gemstones include Aragonite, Azurite-Malachite, Chrysocolla, Gahnite, Mali Garnet, Hiddenite, Idiocrase, Green Opal, Prehnite and Olive Quartz.
Yellow to chocolate-colored Gemstones
The range of warm colors extending from yellow towards the deeper shades of chocolate are particularly loved by those with a rich imagination and a predilection for carrying the colors of the Sun and of energy. There is an ample choice of gemstones, with a wide variety of precious stones in terms of both chemistry and color shade. Amber, for instance, is an ancient organic gemstone, a true natural miracle, available in tones ranging from pale yellow to black, passing through the famed cognac colors. Various varieties of Quartz also offer a vast choice of color, such as Smoky Quartz, its transparent hues caused by aluminum, or the rare and highly sought after Golden Green Quartz, with a chartreuse golden shade. Sphene, with its green to yellowish-green hues, displays every color of the spectrum thanks to its intense fire. A few examples of Sapphire also present these tones, such as the very popular Sunset Sapphire, which recalls the colors of an African sunset, or the Yellow Sapphire, which holds within itself chromatic gradations ranging from pastel lemon to canary orange, tinted by iron. Within the family of the Corundums, Padparadscha Sapphire surely has the rarest and most sought after color, recalling a lotus flower. In particularly high demand and at the height of current fashion are the spicy shades of Cinnamon Zircon and Saffron Zircon, uniting in a single gemstone a wonderful mix of color, adamantine brilliance and intense fire.
These and other examples may be admired here:
Other yellow-chocolate gemstones include Bronzite, Kornerupine, Star Diopside, Epidote, Malai Garnet, Idocrase, Yellow Ortoclase Kunzite, Yellow Opal, Star Sunstone, Cognac Quartz, Quartzite, Sard, Scheelite, Silimanite, Cat’s Eye Silimanite, Star Silimanite and Unakite.
Pink to red Gemstones
Pink, the color of femininity, has the capacity to raise spirits, granting passion and vitality to the wearer. The shades of passion become ever more intense when pink, with its delicate pastel tones, becomes red, the first color in the rainbow. Traditionally associated with love and the heart, red encloses within itself the essence of life: the heart, blood and fire. It is no coincidence that it is loved by strong, proud and fierce individuals. Many gemstones present these chromatic hues; from lavender tones of the Rose de France Amethyst, particularly popular during the Victorian era, to Rose Quartz, with its popular opacity. If color plays an important role in precious gemstones, it is entirely defining for a number of varieties, such as Kunzite, also known as the Iris of California, which displays delicious colors that range from pastel pink to rich orchids, thanks to the presence of manganese. The intensity of the color in the sparkling and extremely transparent crystals have made this precious stone a must-have for every gem collector, factors that also determined the success of the other gemstone discovered by gemologist Georg Frederick Kunz - Morganite, a peach variety of Beryl. Moving towards the reds, Ruby is surely the authoritative representative of this color, both for its fame and because only a few shades of red in Corundum are legitimately called ‘Ruby’. Other shades are referred to using Sapphire names. Rubellite, with a color similar to Ruby, is a variety of Red Tourmaline, with strong crystal pleomorphism, while Pink Tourmaline encompasses lighter and less intense shades of color.
Below are a few examples of well-known red to pink gemstones:
Other red-pink gemstones include Andesite, Red Beryl, Clinohumite, Pink Opal, Pezzottaite and Umbalite
Grouping gems by color is a fairly complex affair, not only because it is impossible to precisely define the hue displayed by each example of a specific gemstone, but also because many gemstones cannot be classified under a single color, for a variety of reasons. First of all, we have precious stones that display particular optical effects, such as color change. Alexandrite is an excellent example of a gemstone with this property, as it may appear green-blue in natural light, but red in incandescent lighting; just like the sought after Zultanite, which can shift from kiwi green to raspberry red. In addition to color change, other phenomena such as adularescence or opalescence give other bluish-white gemstones a surface shine; consider the mysterious rainbow Moonstone or the Opals, which are particularly sought after thanks to their rainbow flash (play of color). Mother of pearl or Labradorite, on the other hand, are in this section because of their iridescence, an optical effect where light is diffracted into the colors of the rainbow by the gemstone itself, resulting in a colorful play that changes depending on the angle of observation. In addition to optical effects, we have the bicolor gems, precious stones which enclose two different varieties within the same crystal, such as the Bicolor Amethyst or the unique Ametrine, a wonderful blend of Amethyst and Citrine. Third, this group includes all precious stones that Nature has not seen fit to give a single distinctive property, making each one even more special and inimitable. The inclusions, colored bands and infiltration of chemical elements foreign to the crystal structure are a few examples of how some of these more unique and unrepeatable gemstones are created. Within the Quartz family, there are many varieties defined based on the inclusions present in the crystal; Tourmaline Quartz is formed when dark inclusions of Tourmaline are inserted into the clear Quartz crystal, while the rare Medusa Quartz is so named for the inclusions of rutile and neon blue dendrites, which recall the body of the jellyfish it is named for.
Sardonyx, a variety of onyx well-loved in Ancient Rome, is a unique mixture of White Onyx and Sard, while Agate, a variety of Chalcedony, owes its characteristic striation to the oxidation of manganese, iron and other minerals.
The most well-known multicolored gemstones are presented in the table below:
Other multicolored gemstones include Bicolor Morganite, Fire Agate, Mabe Pearl, Mookite, Snowflake Obsidian, Rainbow Quartz, Scapolite and Spectrolite.
Colorless and white Gemstones
White has always represented light, simplicity and purity, in both tradition and fashion. A fundamental element enclosing within itself every color of the light spectrum, white is expressed through colorless gemstones in gemology. Selecting a white, or rather colorless, gemstone means ownership of something with incredible transparency. In addition to the famous Diamond, with its inimitable fire and wonderful sheen, nature has many other transparent precious stones to share: White Zircon, with its high refractive index and intense fire, very similar to Diamond but with a different Chemical composition; the rare Petalite, often used for meditation, or the classic White Sapphire. Among these brightly shining precious stones, one of the most recent discoveries in Gemology cannot go unmentioned - White Kunzite, with its inclusion-free crystals and eye-clean transparency. Another gem worth mentioning, Goshenite, a colorless variety of Beryl, is famous for its excellent brilliance and purity, such that it was used in Ancient Greece and Rome to manufacture lenses for eyeglasses. Among the colorless varieties of Quartz, we have White Quartz or Rock Crystal, perfectly transparent and similar to glass, and Phantom Quartz, rich in mineral inclusions, used by the Ancients for divination. Elegant and classic, these stones are essential items for any collector of precious stones!
The most well-known white and colorless gemstones:
Other white and colorless gemstones include Ingelsite, Aragonite, Calcite, Howlite, Fenacite, White Kunzite and Phantom Quartz.