Sapphires – The Birthstone of September – Part 3

Padparadscha

Faceted Padparadscha

Padparadscha is a delicate, light to medium toned, pink-orange to orange-pink hued corundum, originally found in Sri Lanka, but also found in deposits in Vietnam and parts of East Africa. Padparadscha sapphires are rare; the rarest of all is the totally natural variety, with no sign of artificial treatment.

The name is derived from the Sanskrit “padma ranga” (padma = lotus; ranga = color), a color akin to the lotus flower (Nelumbo nucifera).

Natural padparadscha sapphires often draw higher prices than many of even the finest blue sapphires. Recently, more sapphires of this color have appeared on the market as a result of a new artificial treatment method called “lattice diffusion”.

Star Sapphire

Star Sapphire

star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as “star rubies”. Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that causes the appearance of a six-rayed “star”-shaped pattern when viewed with a single overhead light source. The inclusion is often the mineral rutile, a mineral composed primarily of titanium dioxide. The stones are cut en cabochon, typically with the center of the star near the top of the dome. Occasionally, twelve-rayed stars are found, typically because two different sets of inclusions are found within the same stone, such as a combination of fine needles of rutile with small platelets of hematite; the first results in a whitish star and the second results in a golden-colored star. During crystallization, the two types of inclusions become preferentially oriented in different directions within the crystal, thereby forming two six-rayed stars that are superimposed upon each other to form a twelve-rayed star. Misshapen stars or 12-rayed stars may also form as a result of twinning. The inclusions can alternatively produce a “cat’s eye” effect if the ‘face-up’ direction of the cabochon’s dome is oriented perpendicular to the crystal’s c-axis rather than parallel to it. If the dome is oriented in between these two directions, an ‘off-center’ star will be visible, offset away from the high point of the dome.

The Star of Adam is the largest blue star sapphire which weighs 1404.49 carats. The gem was mined in the city of Ratnapura, southern Sri Lanka. The Black Star of Queensland, the second largest gem-quality star sapphire in the world, weighs 733 carats. The Star of India mined in Sri Lanka and weighing 563.4 carats is thought to be the third-largest star sapphire, and is currently on display at the American Museum of Natural History in New York City. The 182-carat Star of Bombay, mined in Sri Lanka and located in the National Museum of Natural History in Washington, D.C., is another example of a large blue star sapphire. The value of a star sapphire depends not only on the weight of the stone, but also the body color, visibility, and intensity of the asterism.

Color change Sapphire

A rare variety of natural sapphire, known as color-change sapphire, exhibits different colors in different light. Color change sapphires are blue in outdoor light and purple under incandescent indoor light, or green to gray-green in daylight and pink to reddish-violet in incandescent light. Color change sapphires come from a variety of locations, including Thailand and Tanzania. The color-change effect is caused by the interaction of the sapphire, which absorbs specific wavelengths of light, and the light-source, whose spectral output varies depending upon the illuminant. Transition-metal impurities in the sapphire, such as chromium and vanadium, are responsible for the color change.

Certain synthetic color-change sapphires have a similar color change to the natural gemstone alexandrite and they are sometimes marketed as “alexandrium” or “synthetic alexandrite”. However, the latter term is a misnomer: synthetic color-change sapphires are, technically, not synthetic alexandrites but rather alexandrite simulants. This is because genuine alexandrite is a variety of chrysoberyl: not sapphire, but an entirely different mineral.

(Information from Wikipedia, the free encyclopedia)

Stay tuned for Part 4 about Sapphires, the Birthstone of September.

Sapphires – Birthstone of September – Part 2

Blue sapphire

Teardrop-shaped blue sapphire

Gemstone color can be described in terms of hue, saturation, and tone. Hue is commonly understood as the “color” of the gemstone. Saturation refers to the vividness or brightness of the hue, and tone is the lightness to darkness of the hue. Blue sapphire exists in various mixtures of its primary (blue) and secondary hues, various tonal levels (shades) and at various levels of saturation (vividness).

Blue sapphires are evaluated based upon the purity of their primary hue. Purple, violet, and green are the most common secondary hues found in blue sapphires. Violet and purple can contribute to the overall beauty of the color, while green is considered to be distinctly negative. Blue sapphires with up to 15% violet or purple are generally said to be of fine quality. Gray is the normal saturation modifier or mask found in blue sapphires. Gray reduces the saturation or brightness of the hue, and therefore has a distinctly negative effect.

The color of fine blue sapphires may be described as a vivid medium dark violet to purplish blue where the primary blue hue is at least 85% and the secondary hue no more than 15%, without the least admixture of a green secondary hue or a gray mask.

The 423-carat (84.6 g) Logan sapphire in the National Museum of Natural History, in Washington, D.C., is one of the largest faceted gem-quality blue sapphires in existence.

Sapphires of other colors

Sapphires in colors other than blue are called “fancy” or “parti colored” (multi-colored) sapphires.

Fancy sapphires are often found in yellow, orange, green, brown, purple and violet hues.

Multi-colored sapphires are those stones which exhibit two or more colors within a single stone. Australia is the largest source of multi-colored sapphires; they are not commonly used in mainstream jewelry and remain relatively unknown. Multi-colored sapphires cannot be created synthetically and only occur naturally.

Colorless sapphires have historically been used as diamond substitutes in jewelry.

Pink sapphires

Pink sapphire

Pink sapphires occur in shades from light to dark pink, and deepen in color as the quantity of chromium increases. The deeper the pink color, the higher their monetary value. In the United States, a minimum color saturation must be met to be called a ruby, otherwise the stone is referred to as a pink sapphire.

More about Sapphires in Part 3.

(Information from Wikipedia, the free encyclopedia)

Sapphire – The Birthstone of September – Part 1

Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminum oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural “fancy” sapphires also occur in yellow, purple, orange, and green colors; “parti sapphires” show two or more colors. The only color corundum stone that the term sapphire is not used for is red, which is called a ruby. Pink colored corundum may be either classified as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs.

Natural sapphires

Sapphire is one of the two gem-varieties of corundum, the other being ruby (defined as corundum in a shade of red). Although blue is the best-known sapphire color, they occur in other colors, including gray and black, and they can be colorless. A pinkish orange variety of sapphire is called padparadscha.

Significant sapphire deposits are found in Eastern Australia, Thailand, Sri Lanka, China (Shandong), Madagascar, East Africa, and in North America in a few locations, mostly in Montana. Sapphire and rubies are often found in the same geological setting.

Every sapphire mine produces a wide range of quality, and origin is not a guarantee of quality. For sapphire, Kashmir receives the highest premium, although Burma, Sri Lanka, and Madagascar also produce large quantities of fine quality gems.

The cost of natural sapphires varies depending on their color, clarity, size, cut, and overall quality. For gems of exceptional quality, an independent determination from a respected laboratory such as the GIA, AGL or Gubelin of origin often adds to value.

(Information from Wikipedia, the free encyclopedia)

More about Sapphires in Part 2 of this series.