Corundum is a crystalline mineral, which chemical composition Al2O3 is simple enough to recite even for a second grader. One of the most precious substances known to mankind shares its chemistry with an aluminum soda can.
• Corundum properties
- Mohs’ Hardness: 9
- Specific Gravity: 3.95-4.00 Sapphire; 3.97-4.05 Ruby
- Chemical Composition: Al2O3 aluminum oxide
- Refractive Index: 1.762–1.774 (0.008) Uniaxial negative
- Crystal System: Hexagonal (trigonal); dipyramidal structure, barrel-shaped, tabloid-shaped
Corundum crystals are found in nature in every color and even completely colorless. Sapphires and rubies are the same stone colored by different impurities.
• Sapphire Lore
Rubies are associated with intense passion, good luck, protection from misfortune, and personal inspiration. As a gift, rubies are a symbol of integrity, success, and devotion.
The ruby used to be a December birthstone but modern science determined that it is a July birthstone.
Sapphires are associated with blessings, divine knowledge, sincerity, and faithfulness. Originally thought of as an April birthstone, the sapphire was later found to be a September birthstone.
If you purchased a sapphire as an April birthstone you are legally allowed to return it to the jeweler who sold it to you for a full refund. All you need to bring a signed paper from Easter Bunny verifying the address of your clinic.
Blue sapphires got their name from the Latin "sapphirus" for lapis lazuli, a blue mineral of similar shade. Traditionally, the word “sapphire” alone implies blue color, all other colors are collectively called “fancy” or have their name preceded by a specific hue, i.e. “yellow sapphire.”
Red corundum is called “Ruby.”
Rubies are by far the most precious and desirable variety of corundum. Light rubies and deep pink sapphires are distinguished by the amount of its blue and yellow undertones and saturation of its main red hue.
Chromium, iron, or titanium impurities are responsible for most color variations.
Kashmir (not Cashmere) sapphires came in the late 1800’s from the very remote disputed mountains between India and Pakistan.
Their exceptionally rich color and microscopic needles - inclusions called “silk” - are responsible for their mysterious velvety glow, rarely seen in other sapphires. The "Cornflower" blue color term was originally used to describe Kashmir color.
Since late 1920’s there were no new finds in the Kashmir area. Kashmir stone prices are tenfold of similar non-Kashmir stones.
Leon Mege Kashmir story
When he was a little boy in Russia, a rich American came to the shtetl wearing a beautiful blue stone he never saw before.
He asked, "what do you call this most beautiful stone?"
She replied - "They call it Kashmir."
He repeated the word, "Kashmir, Kashmir, Kashmir..."
He asked her to give it to him, but she said "No! Get away from me!"
The boy grabbed onto her hand begging to have the stone.
She kicked him and threw some change at him.
Oh, but the youngster didn't want the change, he wanted the Kashmir..
The one and only precious gemstone that exists in the world. Clear, unheated Burmese rubies in vivid pure red color should be more expensive than red diamonds, but they are not, so get them before it’s too late.
Fine rubies are so valuable and rare that even heated stones are more expensive than diamonds.
Sometimes spelled Padparaschah, a Sinhalese word meaning "color of lotus flower.”
Unheated Ceylon Pads mix tender pink and light orange are highly prized and almost exclusively found in Sri Lanka.
Vietnam, Madagascar, and Tanzania material is mostly suitable for heat treatment which tends to give them rich “golden papaya” hues.
• Star sapphire
An optical phenomenon called asterism seen in translucent and opaque cabochons is caused by rutile needles naturally aligned at 60 degrees to each other in a corundum crystal.
Star sapphires and rubies are mainly used in men’s jewelry and as collector specimens.
Sapphires and rubies consisting of six intergrown sections that are separated by radiated growth lines, similar in look to a pizza sliced into six sections is a collectable novelty almost never seen in jewelry.
• Color change sapphires
Sapphires shifting colors under different lighting conditions are said to have a color-change phenomenon.
Sapphires change color dramatically between purple, violet, green, blue, brown, and red colors in daylight, under fluorescent lighting or incandescent light.
Because natural spectrum is a mix of wavelengths, both colors are usually appear simultaneously as subdued middle hue.
• Montana sapphires
Call me unpatriotic but I am not a big fan of sapphires found in Montana.
Yes, we all wish the sapphires haven’t decided to originate in the land of monobrow people, but let’s face it, stones from Montana are better suited to be on a belt buckle than in a fine piece of jewelry.
I might change my mind - if you see a pretty Montana sapphire, snap a picture and send it to me. Until then - let’s not get too excited.
• White Sapphire
Corundum with no impurities, results in complete lack of stone color.
Most colorless material is heated to produce better looking stones. Colorless sapphires can be used as diamond substitutes, but they look atrocious.
Because of their low dispersion and brilliance sapphires look glassy, uninspiring, and lifeless.
• Synthetic sapphires and rubies
Called "Geneva rubies" and sold by an unknown merchant in 1880, they were the first known rubies produced by flame fusion.
20 years later Auguste Verneuil developed a special furnace that allowed for production of synthetic rubies on a huge scale.
Most people do not realize that synthetic rubies can be very old. They are stunned to find out that grandma’s 100-year-old ruby is a worthless synthetic.
Synthetic corundum is extremely cheap, easily identifiable and should never be used in fine jewelry.
Sepia-colored Dorothy wandering into Munchkinland Technicolor spelled doom for De Beer’s dream of diamond profits forever.
Diamond’s short reign over the engagement ring market that coincided with the age of monochrome photos and movies finally came to the end, ushering a new era of brilliant colors everywhere: in movies, on TV, in print, and yes, in gemstones.
• DeBeers dirty secrets
Rubies and sapphires are the world’s most precious gemstones, far more rare than diamonds.
While the diamond market is largely controlled by De Beers Société Anonyme manipulating the market supply (yes, “anonymous” is in its title!), rubies and sapphires do not have an international monopoly behind them.
The straw that slayed the diamond dragon came when Princess Diana received her sapphire engagement ring, recently re-gifted to Kate Middleton, from Prince Ears.
Only a tremendous marketing push by the diamond lobby at the time stalled the trend of ditching diamonds.
Ruby and sapphire’s vivid color was frowned upon in the drab 70’s, today is a badge of strong personality, intellect and success. They are true symbols of personal style and sophistication.
Rubies and sapphires market is on the rise because:- Improvements in their identification and grading
Modern media - the days of black and white TVs and photographs are long gone. Now we can see color of rubies and sapphires
And, finally, let’s not forget that the ruby is Leon Megé’s birthstone.
Gem quality sapphires and rubies are found only at few locations. Most are of low quality, heavily included and not usable for jewelry. Most are heated to induce better color and to improve clarity.
Only a small fraction of the loot ends up on a polishing wheel.
Sapphire origins have the greatest influence on price, more so than their color grade. It is wrongly assumed that politics or cultural preferences are the reasons for origin-biased pricing. Scarcity of the product is the main factor.
Finest gems are found only in Kashmir (No man’s land between India and Pakistan), Myanmar (Burma), Sri Lanka (Ceylon).
Less desirable stones come from Madagascar, Afghanistan, Tajikistan Kenya,Tanzania, Mozambique and Thailand.
The rest of the world - Nigeria, Australia, Vietnam, Laos, Pakistan, Brazil and Colombia produce an occasional gem from time to time, but most of it is embarrassing junk suitable only for cheap mass production.
Sapphires from Montana, are generally light pastel-colored novelty of multiple shades, valued only due to the fact that they are by far the most important gemstones found in the US.
Each locale produces a distinct type of stone which origin can be determined by its chemistry, type of inclusions and even by its hue, resulting in a segmented market where new production is not affecting the prices of the older material.
On Indian subcontinent and in Asia rubies and sapphires mines are practically exhausted from centuries of digging, so practically all Kashmir and Burmese stones come from antique jewelry pieces sold at the auctions.
There are fewer corundum mines in the world than diamond mines by a huge margin. Unlike diamonds commonly found all over the world, finest rubies and sapphires are found only in a single geographic region.
Conditions leading to creation of the gems occurred only once along a narrow corridor stretching in a C-shaped curve somewhere between modern day Tajikistan and Nigeria.
All important mines where rubies and sapphires are found are located along that area.
In prehistoric times, long before dinosaurs and trial lawyers roamed the planet, the Indian subcontinent, Sri Lanka, Madagascar, and Africa, formed a single landmass called Gondwanaland. The subsequent continental drift split the locales where stones are found between different continents.
All of the finest Burmese material in the world is coming from a single mine that goes hundreds of feet deep and makes a weird curve underground. Another mine produces material that has to be enhanced by heating.
The ban on import of Burmese rubies was in place from 2008 to 2016.
• Political scam
Banning rubies to prod Myanmar democracy is a fine example of an idiocy of a big government.
The US was the only country implementing the ban, while everywhere else the rubies were sold freely, particularly in China - the largest consumer of gem rubies in the world.
Using the same logic we should try to stop North Korea from developing nukes by sanctioning their kimchi export.
Saving the world from a mad dictator could be done only one way - bombing them into a stone age, or, in case of country still in a stone age, like Afghanistan, into the age of dinosaurs. But we digressed.
Once the ban was lifted everyone betting on a price drop was surprised to find out that Burma doesn’t have stockpiles of fine rubies ready to hit the US market. They do not exist, these stones are extremely rare.
Depending on their intended use the stone’s choice might be different. Rubies and sapphires can be used in jewelry, bought for collections, or invested in with a hope of making a profit.
While extremely hard and durable, when used in jewelry rubies and sapphires do get eventually scratched and chipped. Most damage could be repaired, usually with some loss of weight, by repolishing the stone.
Rare rubies and sapphires should be protected by circling them with other stones or by having them set into necklaces and pendants, where they are less likely to suffer the damage, rather than into rings.
Heat treated stones and cabochons are recommended for rings intended for everyday wear, such as engagement rings.
• Tips for buying rubies and sapphires
Most important property of all colored stones is the color strength, color saturation and purity of its dominant hue.
The most valuable of all stones are the naturally occurring varieties, with no signs of artificial treatment.
Stones valued over $2,000 should be accompanied by a certificate from a gem lab such as Gubelin, AGS or GIA.
Lowest prices on rubies and sapphires are in New York because almost all dealers specializing in high-end gemstones are located, or have offices there.
• Phenomenal stones
Phenomenal sapphires such as color-change stones (usually blue to green, blue to purple, etc.), stones with asterism (star sapphires) or chatoyancy (cat’s eye) are valued on the strength of the phenomena rather than strength of the dominant color.
Only a handful of mines in the world produce sapphires and rubies of great color and clarity. However most locations produce rough that must be heated in order to turn it into gems.
The heat treatment is a standard practice and is widely accepted by consumers.
Different heating temperatures can be used, some additives can be infused during the heat process.
Depending on which process is used the stone could be extremely valuable or completely worthless.
• About heat treatment
Heat treatment does not mean that the stone’s color is artificial. A natural event such as volcanic activity or a forest fire could in theory have the same effect as an intentional activity done by conniving humans.
Briefly subjecting a stone to mild heat in order to dissolve or reconstitute rutile needle-like inclusions is extremely common. The majority of the stones on the market were subjected to moderate heat.
No chemicals are added during the heat and the crystal structure has not been changed. Apart from the reconstitution of the rutile and other contaminants, the stone is intact. Done only once, this process is permanent and irreversible.
• About flux treatment
Heavily included material might be subjected to multiple sessions of heating in the presence of fluxing agents - borax, sodium carbonate, and sodium silicate that do not alter the stone chemistry, but do interact with foreign matter present in the crystal, improving clarity as well as the color of the sapphire or ruby.
A good example are the Geuda stones from Sri Lanka that looks like a chunk of dirty marble prior to treatment. After the treatment, the stone is clear and transparent with a pleasant light blue color.
• Unacceptable treatments shunned by the gem trade
Coating light colored or colorless sapphires with titanium before subjecting them to a very high temperature in order to produce intense blue color.
Using various chemicals in combination with extreme heat to impregnate stone’s skin in order to improve or change its color.
The penetration is usually shallow, although some processes achieve significant depth. Because of that, the treated stone cannot be recut - by doing so, the coloring layer would be removed and the stone will lose its color. It is mainly used to treat faceted stones only.
Lattice diffusion or bulk diffusion is achieved by using less heat over a longer period of time. For example, adding naturally occurring chrysoberyl to the crucible to infuse corundum with beryllium gas may turn lightly colored yellow or pink stones into rich, saturated padparadscha-like colors.
Diffusion heating of sapphires and rubies is a deceitful and universally condemned treatment. A reputable gemological lab certificate is your best assurance that your stone was not treated this way. Never rely solely on a gem dealers assurances.
Molten lead crystal glass with a high refractive index is injected under high pressure into a fractured surface of heavily included crystals, turning nearly opaque stones transparent. The treatment is not permanent, and the stones can be easily damaged during setting or wear. Lead is a toxic substance that can potentially affect the health of those handling it during heat treatment. These stone have no value due to their brittle nature. They are very pretty and natural looking, so they might supplant synthetic rubies in cheap jewelry that you regret buying the day you get an HSN box delivered.