Ruby / Corundum
Ruby has accumulated a host of legends over centuries. In Sanskrit (the ancient sacred language of India), one of the terms for ruby is ratnaraj, “King of Gems.” People in India believed that rubies enabled their owners to live in peace with their enemies. In Burma (a ruby source since at least 600 AD—now called Myanmar), warriors wore rubies to make themselves invincible in battle. Many medieval Europeans wore rubies to guarantee health, wealth, wisdom, and success in love. As the US birthstone for July, and the world’s best-known and best-loved red gem, ruby still captivates the hearts and imaginations of gem professionals and consumers alike. Large, fine-quality rubies are extremely rare and valuable. But strong worldwide production and an array of treatments have increased availability and put rubies within the reach of most costumers. Common cutting styles for ruby include mixed-cut ovals or antique cushions for translucent to opaque stones. Corundum has excellent toughness, and it’s harder than any other natural gem except diamond. This makes it ideal for rings as well as many other types of jewelry. The name ruby comes from the Latin word ruber, which means “red.” The most expensive ruby color is a deep, pure, vivid red. Stones with a little pinkish, purplish, or orangy red color are also considered rubies, but gems and jewelry professionals make careful distinctions between ruby and pink, purple, or orange sapphire.
Sources
Afghanistan
Kenya
Madagascar
Myanmar
Burma - Considered to produce finest quality rubies
Sri Lanka
Often lighter in tone than rubies from Myanmar or Thailand
Tanzania
Thailand
Mine production declined in the 1990s, but it’s still the world center for treatment and wholesale trade
Vietnam
Hardness & Toughness
Hardness 9 on Mohs scale
Toughness Usually excellent, but stones with certain treatments
or large fractures or inclusions can be less durable
Stability
Environmental Factor & Reaction
Heat: High heat can cause a change in color or clarity, it can also damage or destroy fracture and cavity fillings.
Light: Generally stable, but heat from bright lights can cause oil to leak or dry out.
Chemicals: Can harm fillings and remove oil, soldering flux containing boron, and firecoat made with boric acid powder, will etch the surface of even untreated stones.
Care & Cleaning
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.
Species & Variety
Ruby and sapphire are both Corundum varieties. Generally, the difference depends on a combination of hue, tone, and saturation, but market culture and geography also make a difference. Gems that would be considered pink or purple sapphire in the US are often classified and sold as rubies in some Asian countries. It’s important to keep such regional trade practice variations in mind if you work in different markets, or with an international clientele.
Source: GIA's Library