Designs by Erica Courtney

The Colors Of Tanzanite

Tanzanite’s exquisite color, poised intriguingly between blue and violet, sets it apart from any other gemstone.  Made unique by reflecting both blue and violet (this mix of colors is called pleochroism), tanzanite is formed in a wide range of colors: from light sky blues and lilacs through to deep indigos and royal blue. Some large tanzanites appear to be pure blue, but a closer look will, in most cases, show both colors simultaneously. This is especially true for larger carat sizes, where tanzanite‘s colorful brilliance intensifies, creating a kaleidoscope effect. Many experts consider tanzanite to have the most beautiful color in the world of blue gemstones. Indeed, the vivid blue of a fine tanzanite can put even the most beautiful sapphires to shame.

Colors of tanzanite
Pleochrism in tanzanite -  the ability to show blue and violet.
Crystal showing the three colors of tanzanite. Photo credit - Mim Museum
Smaller tanzanite is usually a lighter color than larger tanzanite.

THE CHEMISTRY BEHIND TANZANITE’S COLOR

Tanzanite owes its celebrated blue and violet color to trace amounts of vanadium and/or chromium, chemicals that were present during crystal formation deep within the earth.

COLOR GRADING

Tanzanite is identified by, and valued for, its two hues: blue and violet. Gemologists describe a tanzanite with a prevalent violet hue as “bluish-Violet” or “bV,” while a blue-dominant tanzanite (with less than 50% violet) is graded as “violetish-Blue,” or “vB.”

THE EFFECT OF LIGHTING

Tanzanite is a true chameleon of a gem. It is very sensitive to lighting, and the same stone can appear very different in varying circumstances. Yellow light, such as incandescent indoor lighting will bring out the violet tones in a tanzanite, while daylight or artificial white light will make the same stone look more blue. For the purposes of standardization, tanzanite is always graded under white light.

SIZE AND COLOR

The size and color of tanzanite gemstones are closely interrelated: larger stones tend to display the deepest colors, while smaller ones are usually less saturated. Tanzanites of intense color occur much more rarely in nature, and, correspondingly, are more valuable. At lower weights, between 1 and 3 carats, tanzanites will usually be pastel to medium colored. As a rule, deeper colors are found in tanzanites weighing 5 carats or more.

Stones over 50 carats are deep blue, and after the 100-carat mark the color shifts to a dark blue-black. Tanzanite of these large sizes and deep colors are extremely rare. In fact, deep violet and blue gemstones only make up some 1% of all tanzanites produced in the world.

TRICHROISM

Tanzanite is strongly trichroic, which means that its uncut crystals radiate three different colors, depending on the direction of viewing: blue, violet, and burgundy. This optical phenomenon is easily visible when a tanzanite crystal is viewed from different angles.

Before cutting, tanzanite is usually subjected to heat treatment that intensifies the blue hues and removes the burgundy color. However, a flash of burgundy can still be present in some large and intensely colored tanzanites, after they have been cut and faceted. Whilst attractive, this flash of color has no effect on value.

Trichroism is caused by tanzanite’s unique crystal structure, and is an entirely natural phenomenon. It is responsible for the stone’s intriguing mix of blues and violets that, in the eyes of many gemstone lovers, makes tanzanite more interesting than its solid blue counterpart sapphire.

COLOR AND VALUE

As with any colored gem, tanzanites in paler hues are more common, and more affordable as a result. Vivid, more intensely colored stones occur much more rarely in nature, and, thus, are more expensive. The deepest tanzanite colors only make up to 1% of the world’s total tanzanite production.

Nevertheless, the color intensity of a tanzanite gemstone does not reflect the stone’s quality, only its rarity. Each tanzanite, no matter what color, is still incredibly rare.