Intro to Rubies

Ruby is July’s vibrant red birthstone. I love using ruby in my jewelry designs because of its great color and its durability. I’m going to tell you a little more about one of the most precious gemstones in the world.


Ruby is the red gemstone variety of corundum, an aluminum silicate mineral. Corundum is found in literally every color of the rainbow. All of the colors other than red are called sapphire. You’re probably most familiar with blue sapphire. Ruby is much, much rarer than blue sapphire, and therefore commands a much higher price.

Corundum has a hardness of 9 on Mohs scale, second only to diamond. It is also a very tough gemstone, giving it great durability for use in all kinds of jewelry.


Ruby forms in metamorphic rocks, including marble, gneiss, and schist. It can also occur in igneous plutonic rocks such as granite and nepheline syenite. Ruby gets its color from the presence of trace amounts of chromium in its crystal lattice when it forms.


Ruby mineral specimens

A Little History

For all of human history, people have adored gemstones for their color and sparkle. Until the 19th century, gemstones were classified by color alone. Any red stone was known as a ruby. With advancing knowledge of mineralogy, it has been discovered that many of the world’s best-known rubies are actually red spinel. For example, the Black Prince’s Ruby in the royal crown of England is in fact a spinel.

Thai vs. Burmese

Rubies are found in many locations, including Sri Lanka, Madagascar, Afghanistan, and Vietnam, but the best known rubies in the world are from Myanmar (formerly Burma) and Thailand. For most of the 20th century, the bulk of the world’s rubies came out of Myanmar. From 1962-1990, the production of rubies from Myanmar was greatly reduced, and Thai rubies took over the world market. The discovery of new deposits in Myanmar in 1990 brought Burmese rubies back again. 

Although color isn’t an absolute indicator of provenance, Burmese rubies tend to be more pinkish in color, and have a violet tinge. Thai rubies tend to be a bit more garnet-colored with an orange tinge. Because of this, rubies are often named “Burma” or “Thai” based on their color, not on their provenance. (Confusing, eh?)

Value Factors

Color is the most important factor that most ruby buyers consider. A pure red is the rarest, and most desirable color. Some collectors prefer a ruby to have just the slightest orange/brown tinge, because they feel that brings out the red even better. In general, collectors favor Burmese rubies over Thai. However, like many things in life, there are exceptions.

Pink vs. Red

In the United States, only a red sapphire can be called ruby. A pink sapphire is called sapphire. But where is the line between red and pink? The distinction can be very fine, and a ruby will fetch a higher price than a sapphire. This joke from the International Gemological Society website sums it up nicely: “whether it’s a ruby or a pink sapphire depends on whether you’re the buyer or the seller.” There have been attempts made to draw clear guidelines, but at the moment, there is no general agreement on where that line stands.

Star Rubies

Some rubies exhibit an optical phenomenon called asterism. It is caused by the presence of tiny needle-shaped mineral inclusions (rutile) that reflect light. The result is that when the stone is cut en cabochon, it displays a bright star-like pattern.

In my mind, a star ruby is just about the most perfect gemstone in the world. It has a lovely color, it’s extremely hard and durable, and it’s always interesting to look at!


Rubies are perhaps the most commonly enhanced gemstones. Nearly every ruby on the market has been heat-treated to improve its clarity and color. Heat-treating does not greatly alter the price of a ruby.

Other treatments that are sometimes done to rubies including a variety of dyeing methods, and fracture filling. Some rubies are treated with polymers or glass to fill in fractures and improve clarity. It’s important to know if your ruby has had these treatments applied, especially when your ruby jewelry requires cleaning and/or repair.




Synthetic rubies are an excellent low-cost alternative for jewelry. Synthetic corundum was first produced in the early 1900s. These early manmade stones were fairly easy to tell from their natural counterparts by a gemologist using a microscope. Some of the more recently produced synthetics are more difficult to differentiate, even mimicking the inclusions found in natural stones.


Both natural and synthetic rubies will fluoresce under a blacklight. Try it for yourself!

U.S. Sanctions

An interesting twist in the recent history of rubies is that the United States put trade sanctions in place against Myanmar, citing human rights violations in that country. The sanctions were first put in place in 2003. They left a huge loophole, though: Burmese gemstones could be sent to another country, cut there, and then imported into the US. This loophole was closed in 2008 when any Burmese jadeite or ruby was restricted from being imported, or bought or sold in the US. This sanction was lifted just last year (7 October 2016) because of the reforms made in Myanmar. We can now buy and sell these beautiful gemstones, and the people of Myanmar have new protections in place. I love a story with a happy ending.

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