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RUBY: PRECIOUS GEMSTONE

Formation

Rubies are only created when very specific minerals are combined together, the most necessary of which is corundum. Corundum occurs when aluminum oxide undergoes a process referred to as isomorphous, in which some of the aluminum ions are substituted with chromium. The red color varies in depth and clarity, but any color variations that deviate from the red varieties are classified as sapphires. Certain minerals can cause a ruby to display a star-shaped light-reflection pattern when the stone is cut onto a cabochon shape. This can often be found in rubies containing traces of minerals such as titanium or rutile.

Corundum is naturally colorless and is one of the hardest minerals known on Earth, with a hardness of 9 on the Mohs scale. When combined with certain elements in trace amounts, corundum produces a wide variety of reds. When the aluminum oxide and trace elements are exposed to high pressure and extreme temperatures, they become the molten mixture in which the ruby crystals will form. When chrome, titanium, iron, vanadium or rutile, or even a combination of the metals, are included in the aluminum oxide mixture, the result is the fiery red color associated with the ruby. Rubies can be uniform in color, have hues of blue, purple, or orange, be bi-colored or even multi-colored, but are always a variety of red.

The crystals form as the molten mixture is cooling. The rate at which it cools will determine the clarity and size of the crystals, as well as how many rubies that will form. When the mixture is allowed to cool over a long period of time, larger rubies are formed. If the mixture cools too quickly, it can limit – or even prevent the formation of rubies. Ruby crystals are formed with straight growth patterns and are hexagonal in shape with smooth sides.

Sources

Burmese rubies tend to be the most sought after variety of ruby because of their superior clarity, hue and saturation. Burma, also known as Myanmar, is known the world over as the finest source of rubies. Top quality rubies, however, also come from Sri Lanka, Thailand, Cambodia, Vietnam, Tanzania, Kenya, Madagascar, Vietnam and Afghanistan.

 

Color

Rubies come in a wide range of natural colors and shades of red. The color range includes pinkish, purplish, orangey and brownish red depending on the chromium and iron content of the stone. The most valuable rubies have a vivid, medium-dark red to slightly purplish red color. Many fine rubies from Myanmar have a slight purple secondary color. Color is mainly caused by the gemstones’ selective absorption of certain wavelengths of light called the body color. In gemstones, color consists of three components:

Hue – the first impression of the color.

Tone – the lightness or darkness of color ranging from light to medium to dark

Saturation – the intensity of a gemstone’s color which is measured from dull to strong to vivid

 

Treatments

In the jewelry industry, it is assumed that rubies have been heat treated unless otherwise specified. Most jewelry-quality rubies are heat-treated to enhance the gemstone’s color and vibrancy.

The Gemological Institute of America and other certification authorities ACCEPT this treatment; it is permanent and will not degrade over time.

Other treatments that are available to the jewelry industry such as lead filling, surface diffusion (surface coloring treatment), oiling, dyeing, waxing, lab created synthetics, or imitations HAVE NOT been performed on any of our gemstones. These treatments are temporary and may require future maintenance.

Ruby is heated to improve its clarity and color. At temperatures above 1700 degrees Celsius, the silk dissolves and improves the color and clarity of the stone. This treatment can turn a colorless ruby into a blue ruby. At lower temperatures, silk can be improved and the color lightened.

Some of our rubies have undergone no treatment of any kind. These rare gemstones that consist of less than 10% of the Ruby market.

SAPPHIRE: PRECIOUS GEMSTONE

Formation

The sapphire (and ruby) are actually corundum. Like most gemstones, the corundum is a colorless mineral formed from aluminum oxide (Al2O3). As with most gemstones, coloring is the result of “impurities” found in the mineral. Titanium and iron impurities produce the sapphire’s familiar blue hue. Sapphires form in feldspathoid-bearing igneous rocks under saturated with respect to silica. They can also form in recrystallized limestone and high-grade metamorphic rocks that are poor in silica and rich in aluminum. This includes marbles and some mica schists.

Sapphires have a trigonal crystalline structure with a hardness of 9. For comparison, diamonds have a hardness of 10, which makes sapphires the second hardest gemstone. Sapphire’s hardness, in part, results from the strong and short oxygen-aluminum bonds. The bonds draw the atoms close, making the crystal very dense.

A gemstone is actually a crystal intrusion in igneous rock. Perfect sapphire crystals form (or grow) in a hexagonal system of bi-pyramids. Picture six-sided pyramids formed base to base. Because of weathering (usually water worn), the crystals that are found are often more barrel shaped, the points having worn off.

Minerals are solid crystalline substances that form by natural and normally inorganic processes. Minerals also have distinct chemical compositions and crystal structure. Sapphire’s composition is aluminum and oxygen, formed in hexagonal bi-pyramids. But it began as disorganized atoms.

Through a complex series of chemical, phase reactions, the aluminum and oxygen atoms are tightly organized in a periodical or homogeneous fashion. From the onset, when the first atoms bond, the mineral attempts to achieve equilibrium with its environment. As such, any environmental change–a change in pressure, temperature, acidity, etc.–alters the inner organization of the forming mineral crystal. This causes flaws, structural defects and inclusions of other minerals.

The crystallization process is divided into two phases–nucleation and growth. Nucleation is that initial formation–a nucleus–from which the crystal will ultimately form. A nucleus is created from randomly scattered materials of a mineral into several joined unit cells. For a gemstone, this occurs on the surface of an impurity –titanium and iron in the case of sapphires. Growth is the process by which the mineral adds successive layers of matter–i.e., adding additional row of atoms. If the conditions for growth are not present, the nucleus can break up.

In igneous environments, pegmatites contain many rare minerals including corundum. The growth of the corundum (sapphire) oxide is helped by the fluidity of the pegmatites’ gas-filled environment. In metamorphic environments, minerals are formed by solid-state transformations at temperatures and pressures different from those that formed the original mineral. Among the oxides, corundum and rutile can form. A rutile inclusion in corundum produces an asterism (the six-rayed starburst effect) in a sapphire cabochon.

Sources

Burmese and Kashmir sapphires are the most sought after varieties, known for their superior clarity, hue and saturation. Kashmir sapphires are mostly found in the resale market, since few sapphires are now mined from that war-torn region in Asia. Burmese sapphires of comparable quality also command high prices. Thailand has its superb quality Kanchanaburi alluvial-mined sapphires which are popular choices for high-end sapphire jewelry. They are relatively rare and of extraordinary beauty.

Since 1996, exceptional quality sapphires have been recovered from alluvial deposits derived from basaltic rocks in Madagascar (an island-nation off the coast of South-East Africa). The crystal morphology, growth patterns, inclusions, absorption spectra, and trace-elements of these Madagascar sapphires are almost indistinguishable from other basaltic-magmatic sapphires – these sapphires are extremely well priced and are often found in high-end exclusive jewelry.

Burma, Kashmir, Sri Lanka, Thailand, Madagascar, Australia, Cambodia, China, Colombia, Malawi, Nigeria, Tanzania, Vietnam and the US are well-known sources of this striking gemstone.

Color

Sapphires come in a wide range of natural colors and shades. Sapphires are available in every color but red. Sapphires in colors other than blue are often referred to as fancy sapphires. The most valuable sapphires have a medium intense, vivid blue color. Black, gray, or green overtones mixed in with the blue will reduce a stone’s value. A more pastel blue would be less preferred than a vivid blue but would still be priced higher than an over dark blackish blue color. Color is mainly caused by the gemstone’s selective absorption of certain wavelengths of light called the body color. In gemstones, color consists of three components:

Hue – the first impression of the color

Tone – the lightness or darkness of color ranging from light to medium to dark

Saturation – the intensity of a gemstone’s color which is measured from dull to strong to vivid

Yellow sapphires are mined in Australia. Green sapphires come from Queensland. From Sri Lanka’s gem-bearing gravels can be found sapphires in hues of royal blue, cornflower blue, pink, yellow, orange (a rare color), violet and gemstones with two or more colors. Yet gem dealers’ prize sapphires of a cornflower blue variety above all. Such stones, with a velvet depth to them, mined in Kashmir, are the most sought after due to their rarity. From Montana are mined a dark blue sapphire with a distinctive metallic sheen. Truly colorless sapphires are rare but are found in Sri Lanka, as are cloudy, milk-colored ones, which are called “geuda.” Heat treatment is used to change the geuda into a blue stone.

Treatments

In the jewelry industry, it is assumed that sapphires have been heat treated unless otherwise specified. Most jewelry-quality sapphires are heat-treated to enhance the gemstone’s color and vibrancy.

The Gemological Institute of America and other certification authorities ACCEPT this treatment; it is permanent and will not degrade over time.

Other treatments that are available to the jewelry industry such as lead filling, surface diffusion (surface coloring treatment), oiling, dyeing, waxing, lab created synthetics, or imitations HAVE NOT been performed on any of our gemstones. These treatments are temporary in nature and may require future maintenance.

Sapphire is heated to improve its clarity and color. At temperatures above 1700 degrees Celsius, the silk dissolves and improves the color and clarity of the stone. This treatment can turn a colorless sapphire into a blue sapphire. At lower temperatures, silk can be improved and the color lightened.

Some of our sapphires have undergone no treatment of any kind. These rare gemstones that consist of less than 10% of the Sapphire market.

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