Sapphires are among the most coveted gemstones that come in a rainbow of colors, presenting jewelry designers with endless possibilities.
Blue is the most common color of a sapphire. The word sapphire not preceded by color means it is blue.
Sapphires are multi-colored crystals of corundum with exception of the red variety called ruby.
The impurities give corundum its many colors: pink, orange, yellow, purple, green, black. The colorless corundum is called leukosapphire. Trace elements that contaminate a corundum crystal cause it to take a different hue. Iron turns sapphire blue, titanium yellow, and chromium purple.
It’s hard to believe that one of the most precious gems, the same metal used to make soda cans.
Sapphire’s essential properties are the color strength, color saturation, and purity of its dominant hue.
Both sapphire and corundum are the same things; corundum is a scientific name for the mineral; sapphire is the gemstone’s name.
Mohs’ Hardness: 9
Specific Gravity: 3.95-4.00 Sapphire
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
The sapphires got their name from the Latin word “sapphirus,” that Romans used for lapis lazuli, a blue marble-like gemstone.
Traditionally, the word “sapphire” alone describes blue-colored corundum. Fancy-colored sapphires have their name preceded by a specific hue, for example, “yellow sapphire.”
Phenomenal sapphires are valued on the strength of the phenomena rather than the strength of the dominant color. They are:
-color-change stones – usually blue to green or blue to purple.
-Stones with asterism (star sapphires)
-Gems with chatoyancy (cat’s eye)
It is impossible to tell the difference without examining the stone with a 10-x loupe. Experienced dealers are able to distinguish slight color variation to form an opinion, which is nothing more than an educated guess. Color zoning is a dead giveaway that the stone is unheated. In general heated and natural stones have exact same luster and brilliance.
Blue sapphire’s top colors are “Royal Blue” and “Cornflower Blue.”
Other valuable sapphire hues are pink, purple, orange, yellow, and green.
Brown and colorless sapphires are the least desirable.
The Padparadscha is an extremely rare color of sapphire. It has a mix of pink and orange hues. The most valuable are Kashmir sapphires with their mesmerizing cornflower-blue color.
Blue is the most valuable sapphire color overall.
Natural sapphires are much rarer than diamonds, but rubies and emeralds are even rarer than sapphires.
There are only a few locations that produce gem-quality sapphires. Most are heated to induce better color and to improve clarity. The rest are of low quality, heavily included, and not usable for jewelry.
Diamonds are found everywhere in the world, but the finest sapphires are found only in few places along the area stretched between modern-day’s Tajikistan and Nigeria.
The right conditions for corundum formation happened at 6–18 mile depth in the earth’s crust roughly 150 to 200 million years ago. Sapphires slowly crystallized out of cooling molten rocks and were carried to the surface by erupting volcanos, earth movement, and erosion. This happened along a narrow crescent-shaped corridor of prehistoric landmass called Gondwanaland. The continental drift tore the giant continent apart, splitting sapphire-rich regions between the Indian subcontinent, Sri Lanka, Madagascar, and Africa.
The most valuable of all sapphires are the naturally occurring varieties, with no signs of artificial treatment. Sapphire origin has the most significant influence on price, more than the color grade. Each locale produces a distinct type of stone whose origin can be determined by its chemistry, inclusions, and hue. The scarcity of stones from a specific region means the price of the old material is not affected by new production at other locations.
Sapphire varieties in order of their value:
-Sri Lanka (Ceylon)
The finest sapphires hail from Kashmir of Led Zeppelin’s eponymous hit song. The mine is long exhausted from centuries of digging, so Kashmirs on the market come from vintage pieces. Kashmir sapphires are usually sold at auctions. All of the finest Burmese material in the world comes 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 finest specimens from Sri Lanka (Ceylon) can also be extremely valuable.
Less desirable stones come from Madagascar, Afghanistan, Tajikistan, Kenya, Tanzania, Mozambique, and Thailand.
Collectors value pastel-colored Montana sapphires for their origin despite the drab appearance and bleak hues.
The rest of the world – Nigeria, Australia, Vietnam, Laos, Pakistan, Brazil, and Colombia produce an occasional gem, but mostly low-grade junk used in cheap jewelry.
Peachy-orange sapphires with creamy pink overtones are precious and rare. The word itself comes from Sanskrit and refers to the color of a lotus flower
The color is poetically described as amber, salmon, beer, and pink roses all in one.
As soon as sepia-colored Dorothy crash-landed into Munchkinland’s Technicolor, diamond reign began to crumble. The age of monochrome photos and black-and-white movies gave way to the world of brilliant colors on-screen, in life, and in jewelry. Princess Diana’s sapphire engagement ring (later re-gifted to Kate Middleton) was a turning point for sapphire acceptance as a legitimate diamond replacement for engagement. As a result, it took a tremendous marketing effort by DeBeers to prevent diamonds’ popularity from crashing.
Sapphires are popular with jewelers, collectors, and investors. While extremely hard and durable, sapphires get scratched and chipped when set in jewelry, rings in particular. Repolishing a stone will make it lose weight but regain a brand-new look. A halo or a diamond cluster is often used to protect a valuable sapphire from wear and tear.
Sapphires are less likely to suffer eventual damage mounted in necklaces or earrings.
Cabochons are practical for those who are less protective of their jewelry.
Sapphires were known to the Etruscans at least seven centuries before Jesus.
In the 13th century, Marco Polo described sapphires in great detail in his “Book of Marvels” while visiting the Island of Serendib (Sri Lanka).
Sapphire was a favorite gem of medieval royalty who believed a sapphire could protect them from harm, envy, and uprising. By the time of the Renaissance, sapphires were coveted by the wealthy and influential for their ability to prevent poverty and increase one’s IQ.
Sapphire is September’s birthstone and commemorates the 5th and 45th anniversary.
Only a handful of mines in the world produce sapphires of striking color and clarity that do not need to be treated. These gemstones are rare. They must be certified by a gem lab to have natural color.
Most rough sapphires come from the ground as translucent pebbles lacking any color. Heating such rocks to turn them into gems is an ancient practice widely accepted as non-detrimental to the stone’s nature. Depending on the heating temperatures and use of additives, the stone could be extremely valuable or nearly worthless.
Briefly subjecting a sapphire to mild heat to dissolve and reconstitute rutile inclusions is extremely common and does not make its color artificial. A forest fire or volcanic activity can have a similar effect.
Most sapphires were subjected to moderate heat, which does not change the crystal structure. This process is permanent and irreversible and has to be done only once.
Any naturally occurring red corundum is called a ruby. Red sapphire does not occur naturally. A red sapphire is a colorless corundum infused with beryllium under intense heat and pressure, turning it red.
A reputable gem lab certificate is the best way to learn about potential treatments.
Never rely solely on a gem dealer’s assurances.
Heavily included material can be heated several times in the presence of fluxing agents – borax, sodium carbonate, and sodium silicate. The chemicals do not alter the stone chemistry but interact with inclusions in the crystal, improving clarity and color.
A good example is the Geuda from Sri Lanka that looks like a dirty piece of marble before but becomes clear and transparent with a pleasant blue color after the treatment.
Coating colorless sapphires with titanium before subjecting them to a very high temperature produces an intense blue color. The penetration is usually shallow, so such stone cannot be recut without removing the colored layer and losing its color. This treatment is mainly used on faceted stones.
Lattice diffusion or bulk diffusion is achieved by using lower heat over an extended time. For example, adding naturally occurring chrysoberyl to the crucible produces beryllium vapors. Light yellow or pink sapphires infused with beryllium turn into padparadschas. Diffusion heating is not an acceptable treatment.
HT+P sapphires are heated at high temperatures under low pressure. As a result, these stones have durability issues. They require separate disclosure under the category of HP. The treatment must be disclosed to consumers using clear language, for example, “sapphire treated with heat and pressure.”
Any unheated sapphire should be accompanied by a certificate from a gem lab such as Gubelin, AGL, GRS, or SSEF.
Clarity and/or color enhanced by heat are categorized into the following grades:
– H – Enhanced by heat (no residues present)
– H(a) – Enhanced by heat – insignificant residues within fissures only.
– H(b) – Enhanced by heat – minor residues within fissures only
– H(c) – Transitional grade between H(b) and H(d). Residues of glass-like materials are present in cavities and/or in fissures. – H(d) – significant and deep-reaching residues present within fissures and cavities filled with lead glass (also known as “Composite Ruby”)
– H(Be) – Enhanced by heat and light elements (such as beryllium).
– PHT (HPHT) – Enhanced by pressure and high temperature (PHT).
– E – minor residues of foreign solid materials may be present within fissures and/or cavities.