“Historically”, ruby and sapphire have been at the top tier of the most important and valuable gems, their importance only surpassed by diamond.
“Historically” is in quotation marks because recent history has witnessed the discovery, availability and use, by jewelry designers, of a host of varieties of beautiful colored gemstones. Collectively, these other gems are of enormous importance to the industry.
In terms of value, top quality larger size rubies are much rarer and much more expensive than top quality larger size diamonds.
Rubies and Sapphires Are One of the Most Prized Gems
To be defined as a “gem”, a mineral (all gems are minerals with a few exceptions) must possess a combination of beauty, durability and rarity. Ruby and sapphire have almost the highest rating in all three categories. This cannot be said for any other gem. For example, a top quality, larger size emerald gets top ratings for beauty and rarity but is one of the least durable gems. A top quality, larger size diamond gets a top rating for beauty but is not as rare as a comparable size and quality ruby or emerald. Diamond is fairly durable but can be broken when struck sharply in a certain direction.
In terms of beauty, a well cut fine quality ruby or sapphire possesses both exquisite color as well as brilliance. Beauty
- color and brilliance
- phenomena- star variety Durability- A combination of hardness (the ability to resist scratching) & toughness (resistant to breakage)
- with 9 on the Moh’s scale, the 2nd hardest gem with very good toughness. Only diamond is harder (10 on the Moh’s scale) and diamond is not as tough. Rarity
- gem quality stones are very rare
What is Ruby and Sapphire?
Ruby and sapphire are the identical mineral species. Both are the mineral species corundum, which is aluminum oxide in a specific trigonal crystal form. It is this combination of the aluminum oxide and the specific crystal form that imparts the durability and outstanding optical properties of corundum.
Pure corundum is colorless. Corundum also exists in a very large variety of colors and the color is dependent on which type of trace (very small amount) chemical impurity is present in the gem crystal.
If the impurity is chromium, the corundum crystal is a rich red and is called ruby.
If the corundum crystal is a color other than red, it is called a sapphire.
If the impurity is a combination of iron and titanium, the corundum crystal is blue and is called blue sapphire. In the trade, if the word “sapphire” is used without a color prefix, it is assumed the reference is to blue sapphire.
Sapphires of a color other than blue are called “fancy” sapphires.
Ruby & Sapphire- A Doubly Refractive Gem
Splits light beam into 2 light rays, except in 1 direction
- each ray has a different velocity and different color
- we see the blend of the 2 colors, in the 2 color directions Directional color change called “pleochrism”
- 2 different color rays in every direction
- except 1 direction has only 1 ray/1 color
Blue Sapphire
September birthstone Colored by traces of iron and titanium History- Known to the ancient Persians and Greeks (“sapphire’ is the Latin word for blue). Indian sources became known to the wider world at time of Marco Polo.
Blue Sapphire Colors
violet Blue- commonly called royal blue- considered top color cornflower Blue- commonly called “Ceylon” blue- considered top color milky & silky Blue Inky Blue- very visible color banding often present greenish Blue- very visible color banding sometimes present
Blue Sapphire Origin
Tanzania- the best are violet Blue (royal blue) Sri Lanka- cornflower (“Ceylon”) Blue to slightly violet Blue Madagascar- the best are similar to Sri Lanka stones Burma- slight violet Blue, some are on dark side, also lighter cornflower Cambodia (“Pailin”)- medium to medium dark (navy) Blue, lighter cornflower Blue Thai- many inky stones, some intense blues and milky & silky ( Kanchanaburi) Australia- mostly greenish to blackish Blue Montana (Yogo Gulch)- lighter “steely” Blue, small crystals Kashmir- silky, but intense blue. Extremely rare and highly prized.
Fancy Sapphires Origin
Pinkish Orange, orangey Pink- “padparadscha”- Sri Lanka, Tanzania Yellow- Sri Lanka, Thailand, Australia, Tanzania Green- Australia, Sri Lanka Pink- Madagascar, Tanzania Purple & Color Change- Sri Lanka, Tanzania; Orange- Tanzania
Ruby
July birthstone, Capricorn Corundum colored red by trace amount of chromium History of Ruby
- Known and prized by ancient Indian Hindus as Lord of the Gems
- The Burmese believed ruby provided protection in battle (700 years ago)
- Ruby was a favorite gem of royalty (crown jewels)
Ruby Colors
Red Deep pinkish Red orangey Red purplish Red brownish Red
Ruby Origin
Burma- the major source of quality rubies. Red, clear pinkish Red, purplish Red
- Mong Hsu- the largest source. Has a bluish core and whitish clouds that must be “burned” out into a beautiful stone. Glassy feather inclusions.
- Mogok- Known for its most prized and rarest pigeon-blood (pure red) color variety. Short rutile silk and well formed crystal inclusions. Vietnam- fine purplish Red, purplish pinkish Red. Thailand- dark Red, brownish Red, Saturn inclusions. Tanzania- highly saturated Red with medium tone (not too light, not too dark). Madagascar- large source of very good color but highly fractured rubies. This is the major source for glass filled rubies. Afghanistan, Cambodia, Kenya, and Sri Lanka- Some quality stones but not major sources. India- low grade stones.
Star Sapphire & Ruby
Six ray stars are the most common. Twelve ray stars are rare. The star phenomenon (“asterism”) is caused by intersecting parallel bundles of fine rutile needles. Each bundle of needles reflects a straight, thin band of light in a direction perpendicular to the long direction of the needle bundle. If a stone has these bundles of needles it must be cut in cabochon style to focus and show the star. A combination of a good star & a good body color is rare and highly prized. Star Sapphires- The best are from Sri Lanka. Other sources are Burma, Thailand and Cambodia. Star Rubies- The best are form Burma. Other sources are Sri Lanka, Thailand, Cambodia and India.
Synthetics, Doublets & Imitations
Synthetic corundum can be identified only by magnification. Synthetic corundum has the same chemical and physical properties as natural corundum. Doublet- A synthetic sapphire or ruby bottom with a thin slice of the natural stone glued on top. When viewed from the top (even with magnification), the stone will appear to be natural. The purpose is deception. Imitation- Any stone that has the same appearance as the stone it imitates but has different properties. Examples: Red garnet and red tourmaline for ruby. Benitoite, kyanite and tanzanite for blue sapphire. Grossular yellow garnet and citrine quartz for yellow sapphire. The purpose is deception.
Faceted & Cabochon Sapphires & Rubies
If a rough stone has good transparency and clarity (not highly included), it is normally cut in a faceted style to impart brilliance to the cut stone.
If a rough stone is not transparent and/or has poor clarity (a lot of inclusions) but an attractive color and more or less uniform color, it is normally cut in cabochon cutting style. Some cabochons can be very beautiful.
The great majority of good quality, center stone size, facet grade sapphires and rubies are cut in the mixed cut style, which is a brilliant cut on the top (crown) and a step cut on the bottom (pavilion) of the stone. The mixed cut style provides a compromise by providing brilliance while saving carat weight. When you shop for a faceted sapphire or ruby, you will have the largest selection to choose from and obtain the best value and combination of size and beauty for your money, if you shop for stones in the mixed cut style.
If you are shopping for a center stone size cabochon sapphire or ruby, you should be aware that these stones were very likely not good enough quality to cut in a faceted cutting style. Therefore this fact should be reflected in the pricing of the cabochon. Star sapphires and star rubies are an exception to this guideline.
Treatments of Sapphires & Rubies
Heat Treatment- The overwhelming majority of rubies and sapphires are heat treated to improve color and clarity. The heat improves clarity/transparency and color by dissolving whitish clouds of rutile silk. In the case of Mong Shu Burmese rubies, borax (sodium borate) flux is used when heating to heal fractures in the stone that reach the stones surface. This improves both the durability and clarity of Mong Shu rubies. The flux helps melt the ruby material in the walls of the fracture which then seals shut upon cooling. Any glassy flux residue on the surface is washed away with acid. The heating also eliminates the whitish rutile clouds and the bluish inner core of Mong Shu rubies and the result is a beautiful red ruby. The overwhelming majority of fine ruby stones of 3 carats and under, in the marketplace are of Mong Shu origin.
It is accepted and assumed in the trade, that unless specifically specified as unheated, that all rubies and sapphires are heat treated. Thus, there is no routine disclosure on lab certificates, stone invoices, stone boxes and envelopes. As such, heat treatment does not “lower the value” of a stone. There is a niche market that will pay a higher price for unheated stones. Thus, it can be said that a fine unheated specimen, of center stone size, will fetch a higher price. This should be verified by lab testing and a certificate.
Beryllium Treatment- This treatment is now in wide use to improve the pale color of yellow sapphires and to turn some yellow sapphires into orange sapphires. Beryllium treatment can also be used to improve the color of some blue sapphires and some rubies. Beryllium treated stones are less valued than non-beryllium treated stones and are (and should be) priced accordingly. It is the accepted standard to label beryllium treated rubies, blue sapphires and orange sapphires, as “beryllium treated.” As the majority of yellow sapphires (and orange sapphires), in the current market, are beryllium treated, it is assumed they are beryllium treated unless otherwise specified.
Diffusion Treatment- The primary use, of this treatment, is to turn a colorless sapphire or pale blue sapphire into a good or top color blue stone. A mix of aluminum oxide powder and iron and titanium trace transition elements is melted and diffused into a thin surface layer of the faceted stone. Although not common, there are diffusion treated rubies. Routine disclosure is a must for this treatment.
Dyeing- Obviously this should be disclosed, but rarely is because the purpose is almost always deception. Found more in rubies than other corundum varieties.
Glass Filling- Glass is melted to fill the fracture cavities of highly fractured stones. This results in a tremendous improvement in clarity and turns commercially non-viable stones into saleable stones. This is most commonly employed with Madagascar rubies, which are highly fractured. Disclosure is a must. Glass filled rubies (and sapphires) have a much lower value than un-filled stones and should be priced accordingly.
Comments (Sapphires & Rubies)
In Summary, it is the combination of beauty, rarity and high durability that makes sapphires and rubies so prized. The beauty of fine faceted ruby and sapphire specimens, is due to the factors of color and the ability (if well cut) to display brilliance. For this reason, most center stone size fine ruby and sapphire specimens are cut in a style that provides brilliance and also saves some weight (the mixed cut style). Of course, there are jewelry design styles that may call for a center stone size fine ruby or sapphire in a cutting style that does not display brilliance (e.g. an emerald cut style).
Some gems, because of their inherent optical characteristics (low refractive index), cannot display much brilliance. An example of such a gem is emerald. A fine emerald specimen is prized for its beautiful color and rarity. However, an emerald cannot display much brilliance because it has a very low refractive index. For this reason, most center stone size fine emeralds are cut in a modified step cut style (specifically, the “emerald cut”). The step cut style cannot display much brilliance but it has the least weight loss of the faceted cutting styles and it displays color exceptionally well.
The listed origin countries for sapphires and rubies and the description of color types of stones, from these origin countries, is a description of the major sources and typical color types from these sources. New deposits are continually being discovered and it is possible to find the different color variations in different locations.
Beauty 
