Tag Archives: garnet

Star Garnet

Star Garnet

Star Garnet

Star garnets, also known as Asteriated Almandine, are a special form of the gemstone garnet. While colored like other garnets they display a reflection-like image of a four or six pointed star caused by the inclusion of rutile needles (an effect known as Asterism).

Star garnet is an unusual form of garnet. Asterism, or the star effect,is associated mostly with star sapphire and star ruby. But in fact a small of group of other gemstones can also exhibit this effect, though specimens are fairly rare. The other star gems include moonstone, quartz, spinel, citrine, diopside, emerald, chrysoberyl and garnet.

The star garnet was designated the official state stone or gem of Idaho in 1967. More precious than either star rubies or star sapphires, the Idaho garnet is usually dark purple or plum in color, with four rays in the star (occasionally the star has six rays, as in a sapphire).

Idaho’s nickname is “The Gem State.” The mountains of Idaho contain veins of gold, silver, lead, zinc, cobalt, copper, and many other rare minerals. Among these rare minerals are gems like the star garnet, jasper, opal, jade, topaz, zircon, and tourmaline.

Star garnets are usually opaque and colored a deep brownish red or a reddish black. Like all star gems, the star effect is caused by inclusions of rutile. But in order to display the star effect the rutile needles must have the right alignment to reflect light in a pattern forming a mult-ray star.

The star effect in most star garnets is subtle and requires the correct lighting to see the star clearly. The best lighting is bright sunlight in the middle of the day where the sun is directly overhead. Using a focussed light like a narrow beam halogen spotlight or a small flashlight that can be focussed to a narrow beam will also work. Then stand directly above the stone and look straight down to see the star.

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Rhodolite Garnet

Rhodolite Garnet

Rhodolite Garnet

When most people hear the name Garnet they think red. But Garnets are more then just a cheap red gemstone. Garnets can come in a wide variety of colors and some can be quite valuable. This guide is a comprehensive look at many different kinds of Garnets and their individual properties.

Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It is found in Cowee Valley, Macon County, North Carolina. Rhodolite comes from the Greek word “rhodon” for “rose-like”.

Rhodolite tends to be lighter in color than most other kinds of red garnet. It can sometimes be confused with ruby because of the similarity in color. The mixture of red and violet in rhodolite is very attractive.By the colouration, and the commonly inclusion-free nature of garnet from this locality, has led to rhodolite being used as a semi-precious gemstone.

The composition of rhodolite is situated between almandite (almandine) and pyrope. Although each stone varies slightly, the mixture is roughly about 55 percent pyrope and 37 percent almandite, along with other elements.


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Mali Garnet, Another Precious

Mali Garnet

Mali Garnet

Mali Garnet, one of the rarer varieties within the garnet group, is a mixture of the species grossular and andradite, therefore it is sometimes called “grandite.”

In the large and varied garnet family of gemstones, there are six common varieties that are recognized based on their chemical composition: pyrope, almandine, spessartite, grossularite, uvarovite and andradite. There are also some mixed members, such as rhodolite garnet, which is a mixture of pyrope and almandite by composition. New hybrid garnets continue to be discovered. In 1994 a mixture of grossular and andradite garnet was discovered in the West African country of Mali, and was named mali garnet. This discovery drew a lot of interest because the grossular and andradite varieties are among the rarest and most valuable garnets. Members of the grossular group include tsavorite and hessonite. The most famous member of the andradite group is the rare demantoid garnet.

Grossular Garnet is found in a variety of colors including, yellow, brown, white, colorless, green, violet red, and orangey red. Stones from the deposit in Mali are typically yellowish green or brownish green. Some gemologists refer to them as a grossular-andradite mixture.

The most valuable mali garnet is the extremely rare chrome green color. Generally speaking, yellow, greenish yellow and yellowish green stones sell for higher prices than the brownish stones. As with any gem, size, clarity and cut can affect the value significantly, with dispersion being a special value factor for Mali garnets.

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Grossularite Garnet

Grossularite Garnet

Grossularite Garnet

Grossular or grossularite is a calcium-aluminium mineral species of the garnet group. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow.

Six common varieties of garnet are recognized based on their chemical composition. They are pyrope, almandine, spessartite, grossularite, uvarovite and andradite. There are also some mixed members, such as rhodolite garnet, which is a mixture of pyrope and almandite by composition.

The grossular group includes the light to medium green grossularite; the cinnamon-colored hessonite; the colorless leuco garnet; a dense opaque green garnet called hydrogrossular; and the rare and valuable deep green tsavorite garnet, colored by chromium.

Deposits of grossularite are found in a number of locations, including Quebec in Canada; Vermont in the USA; Tanzania, South Africa, Kenya and Mali in Africa; as well as in Russia, Pakistan and Sri Lanka. Most of the green grossularite we have seen recently comes from Kenya, while the hessonite comes from Madagascar. Tsavorite garnet is still found in only one geographic location in the world, in the border area of Kenya and Tanzania.

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Demantoid Garnet

Demantoid Garnet

Demantoid Garnet

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet.

It is the most expensive and rare of garnet gemstones, with fine specimens commanding prices of thousands of dollars per carat (thousands per gram).

Demantoid garnets are very rare stones that are only mined a few places in the world. Demantoids are valued for their rarity, their beautiful sparkle and their unique form. The gem was first discovered in Russia and the name is derived from its diamond-like adamantine luster.

While the color of demantoid never equals that of the finest emerald, an emerald-green is the ideal. The color should be as intense as possible, without being overly dark or yellowish green. The color of demantoid is believed to be due to chromium. It should be noted that demantoid’s fire is best seen in the lighter, less saturate gems.

Demantoid by definition is always green, but the exact shade ranges from a very strong yellowish green to nearly the color of a fine emerald. Many stones have a brownish cast. Stones with more intense green coloration are more highly valued, but lighter stones display substantially more fire. The choice of stone color or fire can therefore be a matter of personal preference, with some preferring the less valuable but more lively yellowish-green stones.

While garnets have been known since ancient times, the demantoid variety was not discovered until 1853 in Russia’s western central Ural Mountains. The find was about 110 kilometers north, northwest of Ekaterinburg along the Bobrovka River near the village of Elizavetinskoye. This is an alluvial deposit. A second find is 75 km. south of Ekaterinburg on the Chusovaya and Chrisolitka Rivers southwest of the village of Poldnevaya. Deposits are also found underground up to 3 meters deep in the demantoid place.

In terms of clarity, demantoid is relatively clean. Thus when buying one should expect eye-clean or near-eye-clean stones. Demantoids often contain radiating needle inclusions that are termed “horsetails. Some demantoid garnet is heat-treated to improve the color. The resulting stones are stable under normal wearing conditions.

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Color Change Garnet

Color Change Garnet

Color Change Garnet

Color change garnet, a more romantic name and one that is in a real sense more accurate might be Alexandrite Garnet. This is the first and only known example of blue garnet. For the past fifty years, the statement “garnet comes in every color but blue” would be completely accurate.

Color Change Garnet is one of the most rare, interesting, and phenomenal of all gems. The color change can be intense and equal to the color change of top quality alexandrite. Color change garnets can easily be mistaken for alexandrite. Some of the best stones are from the deposit in Bekily, Southern Madagascar.

Like alexandrite, the Madagascar gem is a night stone. A lady of the evening who puts her best foot forward beneath the light of a flame. The primary hue under incandescent is a beautiful deep grapey purple. Sometimes a tiny bit of red can be seen flashing from the depths of the gem. In finer stones, the afternoon daylight hue is green-gray-blue to blue. A limpid crystalline stone is always beautiful and thus desirable.

As with alexandrite, color change in garnet is in part due to its even balance of transmission wavelength peaks (maxima) in the green/blue vs red spectra, the perception of which is tipped by the type of light source under which the stone is viewed. In daylight which is stronger in the blue green wavelengths, the stone will appear blue; in incandescent lighting which is richer in the red wavelengths, the stone will appear purplish red.

Color-change in any gem material is a complex interaction between many factors, not all of which are completely understood. Color change garnet is especially difficult to photograph. Not only does the color change as a result of illumination under different kinds of light sources but, it also varies as a result of geographical location and time of day.


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Chrome Tourmaline, The Forest Green

Chrome Tourmaline

Chrome Tourmaline

Chrome is a special variety of green tourmaline that owes its vivid green hue to trace amounts of chromium and vanadium. These are the same elements that also impart to emerald and tsavorite garnet their distinctive pure green hues. It should not be surprising, therefore, that the finest chrome tourmaline tends to resemble the finer examples of emerald and tsavorite. Chrome tourmaline is actually a distinct tourmaline variety called chrome dravite, found in East Africa. Chrome tourmaline is often associated with tsavorite garnet; miners will usually concentrate their efforts on tsavorite, as it fetches higher prices.

Chrome tourmaline is a rather special member of the tourmaline group. Found only in east Africa, it is usually found mainly in small sizes. But what it lacks in size it makes up for in colorr. It displays perhaps the richest, most intense green in the gemstone world.

Between chrome tourmaline and tsavorite garnet werefound in the same locations in Tanzania, and both are colored by chromium and vanadium. Miners will usually concentrate their attention on tsavorite, since it has more of an established market and fetches higher prices. But chrome tourmaline, while more scarce, is in many ways the equal of the finest tsavorite.

Like emerald and tsavorite garnet, fine chrome tourmaline is a visually pure “forest” green with slightly yellowish to bluish secondary hues. The blue will normally show itself in incandescent light, the yellow will be more visible in daylight. The same criterion applied to tsavorite garnet and emerald is applicable to chrome tourmaline.


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