Ruby is the name given to the corundum mineral species when it appears in shades of red. Blue and pink shades of corundum are classified as sapphire. Rubies can command the highest per-carat price of any colored stone. This makes ruby one of the most important gems in the colored stone market. In its purest form, the mineral corundum is colorless. Trace elements that become part of the mineral’s crystal structure cause variations in its color. Chromium is the trace element that causes ruby’s red, which ranges from an orangey red to a purplish red. The strength of ruby’s red depends on how much chromium is present—the more chromium, the stronger the red color. Chromium can also cause fluorescence, which adds to the intensity of the red color.
WHERE ARE RUBIES FOUND?
Rubies are found in Myanmar (formerly Burma), the Himalayas, and northern Vietnam. The most renowned rubies typically form in marble (in layers that are distributed irregularly within the surrounding marble). Marble forms as part of the metamorphic (rock-altering) process, when heat and pressure from mountain formation act on existing limestone deposits.
RUBY MEANING & ANCIENT LORE
- The ruby is mentioned four times in the Bible (associated with attributes such as beauty and wisdom, e.g., Proverbs 31:10 “Who can find a wife of noble character? She is far more precious than rubies.”)
- In Sanskrit, ruby is called ratnaraj or “King of Precious Stones”
- People in India believed that rubies enabled their owners to live in peace with their enemies
- In Burma, warriors wore rubies to make them invincible in battle (they didn’t just adorn their armor, they actually inserted them into their flesh to make them part of their bodies)
- Rubies became one of the most sought-after gems of European royalty and the upper classes (worn to guarantee health, wealth, wisdom and success in love)
- To commemorate the 50th anniversary of The Wizard of Oz, jeweler Harry Winston created real ruby slippers set with 4,600 rubies
BUYER’S GUIDE: RUBY
WHAT TO LOOK FOR: COLOR AND CLARITY
Color is the most significant factor affecting a ruby’s value. The finest rubies are pure, vibrant red or slightly purplish red. Too orangy or more purplish in color and the quality diminishes. The highest-quality rubies are vividly saturated yet neither too dark nor too light. If the color is too dark, it has a negative effect on the stone’s brightness. If the color is too light, the stone is considered a pink sapphire, even if the color strength or intensity is high.
Inclusion-free rubies are practically nonexistent. As such, their value depends on how visible the inclusions are. Obvious inclusions or inclusions that reduce transparency or brightness lower a ruby’s value dramatically. If large and prominent inclusions are located under the table facet, they greatly diminish the transparency, brilliance, and value of the stone. Inclusions can also limit a ruby’s durability.
Raw ruby is very expensive, so cutters try to conserve as much weight as possible. Several factors affect the cut and proportion of rubies on the market. A ruby’s crystal shape dictates its suitability for certain cuts however rubies may be found in all shapes and sizes. Pleochroism—the appearance of different colors in different crystal directions—is another factor that influences cut. In ruby it typically appears as red to purplish red in one crystal direction and orangy red in the other. Cutters can minimize the orangy red color by orienting the table facet perpendicular to the long crystal direction. Even so, it’s not always possible to orient a ruby for ideal color return because the potential loss of weight would be too great.
Fine-quality rubies over one carat are very rare, but commercial-quality rubies are commonly available in a wide range of sizes. The price per carat goes up significantly for ruby as it increases in size.
Source: GIA (Gemological Institute of America)