Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

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AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...

Demantoid Garnet Details

Demantoid Garnet

Demantoid garnet is a rare green variety of garnet that was first discovered in the mid-1800s in Russia. It is the most valuable and sought-after member of the garnet family due to its unique combination of beauty, rarity, and durability.

Discovery

Demantoid garnet was first discovered in 1853 in the Ural Mountains of Russia. It was named after its diamond-like luster, which comes from its high refractive index and dispersion. Today, most of the world's demantoid garnets come from Namibia and Madagascar.

Varieties

Demantoid garnet comes in a range of colors, including green, yellowish-green, and brownish-green. The most valuable demantoids are a pure green color with no brown or yellow tones. Demantoids may also contain inclusions of needle-like crystals that resemble horse tails, which are highly prized by collectors.

Horse Tail Inclusions

Horse tail inclusions are a rare and highly prized feature of some demantoid garnets. These inclusions consist of needle-like crystals that radiate out from a central point, resembling the tail of a horse. They are caused by mineral inclusions that form during the gemstone's growth process, and are unique to demantoid garnets.

Russian Demantoid Garnet

Russian demantoid garnets are highly sought-after by collectors due to their superior color and clarity. Russian demantoids are known for their bright green color and lack of inclusions, making them some of the most valuable demantoids in the world.

Pakistani Demantoid Garnet

Pakistani demantoid garnets are a recent discovery and are highly valued for their unique combination of color and clarity. They are known for their bright green color and high transparency, which makes them ideal for faceting.

Irani Demantoid Garnet

Irani demantoid garnets are known for their bright green color and high clarity. They are typically smaller than other demantoids, but are highly prized for their beauty and rarity.

African Demantoid Garnet

African demantoid garnets are typically larger than other demantoids and are known for their bright green color and high clarity. They are often found with inclusions, but can still be highly valuable due to their size and beauty.

For deep study please visit the following link https://aggemologist.blogspot.com/2020/06/types-of-garnet-and-its-identification.html

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