Collector’s Guide: Blue Sapphires
We are thrilled to present our first collector’s guide and exhibition showcasing Sapphires. While by no means comprehensive, this overview will touch on the gemological properties of sapphires, quality factors, common treatments and significant origins.
Our hope is that you develop a general understanding of the complexities of the sapphire market. Archeological evidence shows that sapphires were collected by the Etruscans over 2500 years ago and was also prized in ancient Rome, Greece and Egypt. They were once revered as the stone of royalty and believed to keep kings safe from harm and envy. In more recent centuries it has been thought to represent sincerity, truth and faithfulness. They are truly fascinating and alluring gemstones.
Sapphires are a variety of the mineral corundum with a chemical composition of Aluminum Oxide, Al2O3. Corundum can only form in an environment free of silica. Naturally formed corundum is very rare as Silica is the 2nd most common element found in the earth’s crust. Sapphire is the second hardest gemstone on earth, measuring a 9 on the MOHS scale of hardness, only outdone by the diamond which scores a 10. Sapphires are formed in every gem color except red. Red corundum is known as ruby. Blue sapphires develop in the earth’s crust under great heat and pressure while in the presence of the blue coloring elements of iron and titanium. Gemological identification of sapphire is possible by reading a refractive index of 1.762-1.77 on a spectroscope. The specific gravity of sapphire is 4.00, which is approximately twenty percent heavier than a diamond. This means a sapphire weighing 1.2 carats will appear to be the size of a one carat diamond.
When considering a sapphire, color is king. The most important element in pricing a blue sapphire is color saturation; the hue directly reflects the value of the stone. Of course, personal preferences are an important factor in making a choice, but when assigning value to a stone, naturally colored sapphires in a medium to medium-dark tone with excellent pure blue saturation are the most rare and most valuable.
Unlike diamonds, where inclusions are looked upon as flaws, inclusions in sapphires are valuable tools for revealing origin identity and confirming natural formation. While major eye visible inclusions reduce the value of a stone, certain inclusions, visible under magnification, do not undermine the value. In fact, these inclusions can increase value if they point to the most prized origins or confirm the gem to be an untreated specimen.
A very important factor when purchasing a gemstone is an understanding of the treatments subjected to a stone and how those treatments affect value.
For centuries many sapphires have been exposed to heat, in an effort to improve what nature created. In the 19th century, pale imperfect sapphires were heated to heal inclusions and remove all color, rendering the stone transparent and colorless. These transformed stones would then be used as diamond simulants. By the mid 20th century, the same pale material previously heated to become colorless, was being treated with improved technology. To deepen stones to a more desired blue color, they are subjected to extreme high temperatures and exposed to titanium and iron in a controlled environment. Although this remains a somewhat unpredictable process, the desired result can transform pale sapphires into the finest colors possible in nature.
Many other modern treatments are applied to sapphires including beryllium coatings, which apply a thin layer of color to the stone. There are many other lesser-used treatments, such as fillers used to improve clarity.
Some treatments alter the natural crystal structure and can destroy internal inclusions. When a stone has been compromised, gemologists can identify the damage by reading altered internal characteristics. While these treatments do make insignificant material more marketable, treatments actually have a negative affect on value when compared to their natural counterparts. Ultimately, the treatments are creating an abundance of new material that is pretending to be precious and rare
The staggering truth is, roughly 90 percent of the sapphires on the market today have been treated in some way. This makes understanding treatments extremely important for the buyer and collector. The difference in the true value between a treated and untreated gemstone is substantial.
Many laboratories exist to give certifications to authenticate origin and treatments of gemstones. The labs use high tech equipment along with expert gemologists to offer their educated opinions on the details of gemstones. In the United States, the Gemological Institute of America (GIA) and the American Gemological Laboratory (AGL) are both very respected and commonly used for colored stone grading and certification. In Switzerland, the SSEF and Gübelin Laboratories offer certificates for colored stones and are considered authorities. It is common that high value sapphires have multiple certificates to guarantee a stone, particularly with Kashmir sapphires. The sapphires we offer will be accompanied by at least one of these laboratories certificates.
An understanding of the classical and modern sources is important factor in an education on sapphires. Sapphires have been found in many parts of the world. Today the world’s most abundant source of sapphire is Australia. Stones from certain sources display desirable properties unique to their source. This section will provide a framework of the major sources and the basic attributes of each source. While stones may have a crossover in appearance, gemologists use internal characteristics to distinguish the origin of most stones. The rarity of origin along with the specific attributions dramatically impact the value of a sapphire
There are two major geologic sources of sapphires, metamorphic and magmatic. Sapphires from Sri Lanka, Montana, Burma and Kashmir were formed within metamorphic conditions of intense heat and pressure over great periods of time. Sapphires from Thailand, Australia, Africa and China were formed in magmatic conditions and known as basaltic sapphires. Madagascar origin sapphires are unique in that both geological sources are found there.
Kashmir is located in Northern India at roughly 15,000 feet in elevation. It is a remote part of the Himalayan Mountains known as the Zanskar range. This source of sapphires is legendary. In 1881, landslides laid bare the rocks beneath the soil, and disclosed the presence of the gems. The journey to the mine was quite dangerous and challenging. It started by traveling rivers to cross a rope bridge which was elevated 11,550 feet in the mountains. The Chinab River ran through deep and narrow canyons, which made traveling even more difficult. Just this 24-mile portion of the journey took over 5 days. From the years 1882 to 1887, when not covered in snow, throughout the summer months the mines were worked day and night until they were depleted. For thirty more years, unsuccessful efforts were made to find additional deposits in the area. After great effort, only poor specimens were found and the mines were officially abandoned in 1927. This fascinating history makes Kashmir the scarcest origin for fine sapphires. The stones are highly sought after because they are the epitome of a perfect specimen. They have a superior deep blue hue to them with a mysterious and almost sleepy quality. Some gem enthusiasts describe this attribute as ‘blue velvet’. Stones certified to be of Kashmir origin achieve substantially higher prices as compared to all other origins of sapphires.
Sri Lanka - Ceylon
Sri Lanka is the modern name bestowed upon the island of Ceylon. The island was known as Ceylon from 1796–1972, while under British rule. Prior to British colonialism the island had many names, changing with each ruling party. In the sapphire trade, stones from this region are referred to as “Ceylon”. They are usually found in Limestone deposits embedded in granite. Mining typically occurs at depths of 3 to 33 feet. Ceylon has been one of the oldest sources of sapphires with evidence of this origin found from antiquity. While production is waning, Sri Lanka remains an important source for many sapphires in the gemstone market today. The color of Ceylon sapphires is typically a beautiful shade of cornflower blue. On rare occasions they can achieve the finest deep royal blue. Ceylon sapphires often have under tones of grey or violet. Once mined, most stones are faceted locally while many finer specimens are exported or re-cut in Europe and America to improve the shape and proportions of the stone.
Burma is famous for producing the most beautiful rubies in the world. While the blue sapphires are not as well known, they are also quite fine. On average, the sapphires from Burma are more pure blue than Ceylon stones. Distinguishable by a fine rutile silk found in many Burmese sapphires, these stones are typically saturated rich blue without any of the classic undertones of the sapphires from Ceylon.
“Blue pebbles” were discovered while prospectors were searching for gold in 1878. It was not until 1894 that the "blue pebbles" were recognized as sapphires. Sapphire mining began in 1895 after a local rancher sent a cigar box of gems he had collected to an assay office, which in turn sent them to Tiffany’s in New York, where an appraiser pronounced them "the finest precious gemstones ever found in the United States.” These lively stones are typically small in size and have a fine steely blue color. The finest specimens have been mined at the Yogo Gulch in central Montana. Other small mine operations exist in Montana but the quality has been inferior to the ones mined at Yogo Gulch. Most stones from these other sources require heat treatment to be marketable. An English company was the first to commercially produce from the area and many of those stones were sent to Europe to be faceted and sold throughout England and the European continent. Montana specimens are typically small making untreated Montana sapphires over one carat in size quite rare and valuable.
Sapphires were discovered in Madagascar off the southern coast of Africa in the late 1990’s. It has become a major producing source of fine sapphire material. This rare find of a new material source is producing gems that give the classic sources a run for their money. Today, the market is placing the value of these stones between that of Ceylon and Burmese stones. However, in recent years some very fine specimens have actually been confused for Kashmir sapphires, making them a good value. The finer stones are found in the metamorphic deposits in southern Madagascar.
Australia, Thailand, Africa, China, & Northern Madagascar
These are some of the locations that produce sapphires from magmatic geologic conditions. These sapphires are known as “basaltic” and formed slowly in cooling magma flows under the earth’s crust. Basaltic stones have a darker, sometimes inky appearance. While they can achieve a pleasant blue color, they are typically darker than ideal with black undertones. Basaltic stones are often untreated but are generally considered less valuable than the brighter metamorphic examples.