Ruby is the most valuable variety of the mineral corundum because of its rich, red color. It can command the highest price per carat of any colored stone, making it one of the most important gem stones.
Corundum is colorless. Chromium is the trace element that causes a ruby’s red. The stronger the chromium, the stronger the red color, which can range from an orange-hued to a purple-hued red.
The name ruby originates from the Latin word for red – ruber. Ruby has accumulated many legends through the years. In India, it was believed that rubies allowed their owners to live in peace; Burma warriors were invincible in battle if they inserted rubies into their bodies; Europeans in medieval times wore rubies to gain wealth, wisdom, good health, and love; Hindus believed the possessor of a Brahmin ruby to have perfect safety, and ancient Hindus believed that rubies offered to the god Krishna afforded them rebirth as emperors. In ancient Sanskrit, ruby was known as the king of the precious stones.
Rubies are mentioned in the Bible four times, making it the most precious of the 12 stones created by God.
The appeal of rubies is as prevalent today as in the past. Ruby symbolizes passion, making it a perfect romantic gift. The lush, vibrant red color of rubies signifies wealth and success.
What to look for
Vibrant red to purplish red color, with vivid color saturation, indicates the finest ruby. However, the highest quality ruby’s color must not be too dark or too light. The more orange hue in a ruby means the quality is lower.
Rubies are expected to have inclusions. The value of the stone is determined by how visible the inclusions are.
Most rubies are cut in a flat, hexagonal shape. The cut is determined by the ruby crystal’s shape.
The higher the carat weight of a ruby, the higher the price.
Tips & Advice
- Work with a jeweler you trust. Look for a jeweler with gemological credentials who can demonstrate knowledge about judging the quality of a ruby.
- Don’t confuse origin with quality. Fine-quality rubies can come from several countries. Where the ruby originates does not necessarily determine the quality.
- Ask if the ruby is treated. Most rubies have been heat treated; some rubies have been modified by color diffusion or fracture filling to alter their appearance. Ask for this type of information in writing, and inform your jeweler of the modifications any time you are having repair work done on the ruby.
- Request a lab report. Gemological Laboratory of America can produce a report that confirms the ruby is natural, and identify if the stone has been treated in any way.
Caring for ruby
Ruby is an incredibly durable gemstone if there are no treatment-related durability concerns. – Courtesy Jan Goodman Co.
Hardness and toughness
Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or difficulty with which one mineral can be scratched by another. But the Mohs scale is deceptive. The steps between the minerals are not evenly spaced. For example, diamond is only one number away, but it’s many times harder than gems in the corundum family.
Corundum (ruby and sapphire) is relatively hard—9 on the Mohs scale. It has excellent toughness and no cleavage, which is a tendency to break when struck. This makes it a great choice for rings and other mountings subject to daily wear.
Care and Cleaning of Rubies
Ruby is a durable gemstone if not modified by treatment or filling.
Corundum is stable under normal wearing conditions. Fracture-filled, cavity-filled, and dyed stones can be damaged by even mild acids like lemon juice.
Warm soapy water is always safe. Ultrasonic and steam cleaners are usually safe for untreated, heat-treated, and lattice diffusion treated stones. Fracture-filled, cavity-filled, or dyed material should only be cleaned with a damp cloth.
Treatment and durability considerations
Untreated ruby and even heat-treated ruby are very durable. Stones that have undergone diffusion treatment may have treated color that penetrates the entire stone, while others have very shallow color penetration. For stones with shallow color penetration, surface damage or re-cutting can remove color.
There are large numbers of fracture-filled rubies in the market and they require greater care than untreated, heat-treated, or lattice diffusion treated ruby. The glass can be damaged through contact with a variety of chemicals, causing changes in the high-lead content glass.