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Ruby Buyer's Guide

The beauty, rarity and historical mystique of rubies are undeniable. The earliest record for the mining of rubies goes back to more than 2,500 years ago in Sri Lanka. The ancient Hindus were enchanted by the color of rubies and they considered them to be the Rajnapura or “King Of Gems”.


Identical in every attribute to sapphire, except for their red color hues, the term “ruby” can only be applied to the red varieties of the mineral known as corundum, which is second only to diamond in hardness.

Color is the single most important factor in determining a ruby’s value. As if to emphasis this point, even the name ruby is derived from the Latin word for red ruber. While color preferences are subjective, traditionally the ideal ruby color displays the intensity and richness of bright crimson without appearing too light or dark. Still beautiful within their own right, rubies that appear dark and garnet-like, or those that are light in color and are perceived as pink, generally offer the consumer better value.

It is generally recognized that the best ruby colors possess a captivating, intense, almost electric red effect due to fluorescence. Appearing super-charged, these intense colors are most often seen in Mogok rubies.



Rubies generally look best viewed with incandescent light or daylight (particularly around midday). Avoid fluorescent tubes, which have virtually no output in the red end of the spectrum, and so cause ruby to appear grayish.


In terms of clarity, ruby tends to be less clean than sapphire. Buyers should look for stones which are eye-clean, i.e., with no inclusions visible to the unaided eye. In the case of some rubies, extremely fine silk throughout the stone can actually enhance the value. Many rubies also display a strong red fluorescence to daylight, and this adds measurably to the beauty of this gem.
While a certain amount of silk is necessary to create the star effect in star ruby, too much silk desaturates the color, making it appear grayish. This is not desirable.

Shape & Cut

Faceted rubies (those with flat polished faces) are found in a variety of shapes and styles. While ovals and cushion cuts are most commonly seen, other shapes such as emerald cuts and hearts are not uncommon.

Slight premiums are levied upon round cut rubies due to the usually higher carat weight loss of expensive rough crystal during cutting. Conversely, discounts are often applied to the value of both pear and marquise cuts.

A perfectly cut ruby should exhibit good symmetry and polish conditions: facets should be aligned straight in relation to the gem’s girdle and also to each other, polish condition should be good with no visible surface pits or polishing lines.

It could be argued that cabochons are the most common form of cut seen in ruby. Often used to develop and display asterism in star rubies, cabochon cuts are most regularly applied to those rubies whose clarity is not ideal for faceting. Well-cut proportioned cabochons with good symmetry, which are semi-transparent with smooth un-cracked domes, are the ideal.

Stone Sizes

Large rubies of quality are far more rare than large sapphires of equal quality. Indeed, any untreated ruby of quality above two carats is a rare stone; untreated rubies of fine quality above five carats are world-class pieces.


Ruby may display asterism, the star effect. Fine star rubies display sharp six-rayed stars well-centered in the middle of the cabochon. All legs of the star should be intact and smooth. Just having a good star does not make a stone valuable. The best pieces have sharp stars against an intense crimson body color. Lesser stones may have sharp stars, but the body color is too light or grayish. On occasion, 12-rayed star sapphires are found. Inexpensive star rubies come mainly from India.


The original locality for ruby was most likely Sri Lanka (Ceylon), but the classic source is the Mogok Stone Tract in upper Burma. Fine stones have also been found in Vietnam, along the Thai/Cambodian border, in Kenya, Tanzania, Afghanistan, Pakistan, Yunnan (China) and most recently, Madagascar. Low-quality rubies also come from India and North Carolina (USA).

Carat Weight

Large rubies of high quality are the rarest and most highly prized of all gemstones. Rarer than diamonds or sapphires of an equal quality and size, any high quality piece above five Carats is considered to be extremely rare and is almost priceless.

As the Carat weight of a ruby increases, so does its price per Carat. As large rubies are many times rarer than smaller rubies, per carat prices increase disproportionately - a three Carat rubyis worth many times more than three one Carat rubies of a comparable quality.

Prices for ruby increase in stair-like steps when in excess of certain significant Carat weights. For example, a 2.02 Carat ruby commands a higher per Carat price than a 1.98 Carat ruby, despite a negligible difference in actual size. Ruby pricing, like that of nearly all other gems, suffers from a “non-linear-scale of increments”.

The Use Of Heat

Most rubies seen on the market today have been subjected to high temperatures in an age-old practice that is said to have originated in Sri Lanka some 2,000 years ago.

Rubies are heated at high temperatures to improve their clarity and to intensify their colors. Without this practice, we would see fewer rubies on the market today, at far higher carat prices due to restricted and narrowed supplies. Heating rubies makes otherwise expensive gems, more accessible and more affordable.

The proportion of unheated rubies on the market is very small and is widely thought to be less than 0.5%. Although no more beautiful, their rarity makes them highly collectable and prices are set at a premium, sometimes fetching triple the price paid for an equivalent heated ruby. When purchasing high quality rubies, please be aware that unheated material is almost non-existent, as a result, always purchase from a reliable supplier who guarantees their gemstones or have the seller’s claim verified by a qualified expert.

Properties of Ruby (a variety of corundum)


Hardness (Mohs)

Specific Gravity

Refractive Index

Crystal System





1.762–1.770 (0.008) Uniaxial negative

Hexagonal (trigonal)

Various shades of red.
Ruby is colored by the same Cr+3 ion that gives alexandrite and emerald their rich hues.






Synthetic available?

Strongly dichroic: purplish red/orangy red

6 or 12-rayed star

No special care needed

Frequently heated; occasionally oiling, dying, surface diffusion


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