Color Change Garnet Gemstone Information


Color Change Garnet is one of the most rare, interesting and unique of all gemstones. Any gem that changes color is a rare find and coveted by collectors. Garnets exhibit the widest variety of color changes in the gem world, with almost every hue exhibited.  It is commonly said that garnets come in every color of the rainbow except blue. This is still true in natural light, but there are recent discoveries of color-change garnets that turn blue in artificial light.
 
The color change can be intense and equal to the color change of top quality alexandrite. In fact color change garnets can easily be mistaken for alexandrite. Some of the best stones are from the deposit in Bekily, Southern Madagascar. Stones from this mine are well known for their strong alexandrite like color change.
 
Color Change Garnets are very unusual. Being a singly refractive gemstone it is surprising that it has the ability to effect a color change at all. The change comes when putting the stone under 2 different types of light. For example, in daylight a color change garnet may appear blue/green while under incandescent light it changes color to pink-red.
 
The price and value of Color Change Garnet vary according to the size and quality of the gemstone. Color, clarity and the degree of color change are all important factors in valuing top grade Color Change Garnet.
 
Why Buy Loose Gemstones Instead of Pre-Set Jewelry?
 
There are many reasons, but basically it comes down to value and choice...

When buying your Color Change Garnet gemstone loose instead of a pre-set stone, you can be sure you are getting the best value for your money.  Loose gemstones are less expensive, a better value, and you can really see what you are paying for.  The most important part of getting the right price and finding the best value is to first see what you're getting.  A jewelry setting will hide the inclusions inside a gem, and can deepen or brighten its color.  With a loose stone you can much more easily inspect the gem and see it for what it really is.  In this way you can get a better idea of its true worth and be sure you are paying a fair price.

Color change garnet earringThe second advantage of buying a loose gemstone is choice.  You are free to pick the exact color, cut, shape and variety of the stone for the setting of your dreams, be it yellow gold, white gold, platinum or silver; prong set or bezel set with diamond accents.  You can experience the joy of creating your very own, one-of-a-kind jewelry design. Choose from a variety of jewelry settings and styles to create a completely original presentation that will perfectly suit your individual gemstone and will be as unique as you are!
  
 
Attributes

Origin Madagascar, Tunduru, Tanzania, Ceylon (Sri Lanka), Norway and the United States.
Color Light bluish green, blue, green and purple in white light, and light red to purplish red and pink in incandescent lighting.
Refractive Index 1.73 - 1.81
Chemical Composition [Mg3 + Mn3]AL2(SIO4)
Hardness 7 - 7.5
Density 3.65 - 4.20
Crystal Structure Cubic
  
 
Color change garnets are mostly pyrope and spessartite in composition. Except for the color change, they are identical in properties to the Malaia variety.

Color-change garnets have a refractive index of between 1.73 and 1.81 and no birefringence. The refractive index (RI), measured using a refractometer, is an indication of the amount light rays are bent by a mineral.  Birefringence is the difference between the minimum and maximum RI.

There are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, and uvarovite, grossularite, andradite, which are all calcium (metal) silicates.  In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.

Garnets as a group are relatively common in highly metamorphosed rocks and in some igneous formations. They form under the high temperatures and/or pressures that those types of rocks must endure. Garnets can be used by geologists as a gauge of how much temperature and pressure the rock has endured. Garnets are greatly variable in colors and varieties, though, and many of these are both rare and beautiful, producing genuinely precious gemstones. Some garnets are truly unique in the mineral kingdom and have much to offer as both gemstones and mineral specimens.

The general formula for most of the garnets is A3B2(SiO4)3. The A represents divalent metals such as calcium, iron, magnesium and/or manganese. The B represents trivalent metals such as aluminum, chromium, iron and/or manganese and in the rarer garnets; vanadium, titanium, zirconium and/or silicon. The general formula for a couple of rarer garnets (hibschite and katoite) is A3B2(SiO4)3-X(OH)4X. The main differences in physical properties among the members of the garnet group are slight variations in color, density and index of refraction.

Most gems have a crystalline structure. Crystals have planes of symmetry and are divided into seven symmetry systems. The number of axes, their length, and their angle to each other determine the system to which a crystal belongs.  Garnets are isostructural, meaning that they share the same crystal structure. This leads to similar crystal shapes and properties. Garnets belong to the isometric crystal class, which produces very symmetrical, cube-based crystals. The most common crystal shape for garnets however is the rhombic dodecahedron, a twelve sided crystal with diamond-shaped (rhombic) faces. This basic shape is the trademark of garnets, for no other crystal shape is so closely associated with a single mineral group like the rhombic dodecahedron is with garnets.

Most garnets are red in color, leading to the erroneous belief that all garnets are red. In fact a few varieties, such as grossular, can have a wide range of colors, and uvarovite is always a bright green. As a mineral specimen, garnets usually have well shaped and complex crystals and their color and luster can make for a very beautiful addition to a collection.
 
 
The Complexity of Color Change Garnets
 
The chemical composition of garnet can vary widely, so long as the size of an atom can be accommodated within the structural lattice. An intermediate member of a garnet series is often said to contain a mixture of the molecules of the end members of the series. This is a simple way to say that the ratio of chemical elements in the chemical composition changes in a progression from one end member to the other.

In the pyrope to spessartite series, the elements involved are magnesium and manganese. In the chemical composition of pure pyrope, there is no manganese. If manganese is present in the surrounding matter as a garnet crystal develops, then it may occupy an atomic site in the lattice that could be occupied by a magnesium atom. It is thus said that a manganese atom has replaced an atom of magnesium. As the ratio of manganese to magnesium increases, the series grades from the end member pyrope to the end member spessartite until manganese has completely replaced magnesium in the chemical composition. It is important to remember that atoms of other elements can occupy sites in the atomic lattice. The color-change garnets are excellent examples of the complexity of the chemical make-up of the garnets.


Color           

Any gem that changes color is a rare find and sought after by collectors. Garnets exhibit the widest variety of color changes in the gem world, with almost every hue exhibited. It is commonly said that garnets come in every color of the rainbow except blue. This is still true in natural light, but there are recent discoveries of garnets that turn blue in artificial light.
 
The color change is due to a freak of nature in this variety of garnet. It is a pyrope-spessartine species, that changes hue based upon the source of light. Depending on its position and what kind of light it is exposed to the gemstone’s color will change from red to green.

Some people call this a mood stone because it displays so many different colors during the course of the day. In sunlight a tiny bit of red can be seen flashing from the depths of the stone. In daylight it may appear green, gray or even blue. Under direct light it appears as purple as a grape colored amethyst. In candlelight it has more of a bloody color.

However the ability for the stone to display different colors is not due to the wearer’s mood, although they are sold as mood rings by some retailers, it is due to light wavelengths. Typically one color is seen in light sources which are rich in the blue end of the spectrum like fluorescent or natural daylight, and another in light sources which is rich in red wavelengths like incandescent light.


Cut

Color Change Garnets are often cut as round brilliant, cushion, oval and fancy cuts. Cabochon-cut color change garnets are not often seen.

The lack of pleochroism means that orientation is not a problem and the equidimensional shape of the rough generally provides good yields from rough to cut.


Treatments

Color Change Garnets are not normally heated or enhanced in any way.
 

Sources 

East Africa
 
The color-change garnets found in East Africa involve a mixture of the molecules of spessartite and grossular, with a substantial amount of chrome and vanadium incorporated into the chemical composition. Spessartite is the major component, but grossular can be almost half the composition, with almandine or pyrope also in the mix. In the Color Encyclopedia of Gemstones, Joel Arem gives the following information. The spessartite-grossular-almandine color-change garnet has a refractive index of 1.773, with a density norm of 3.98. It appears greenish-yellow brown in transmitted fluorescent light. In reflected fluorescent light, it changes to purplish-red. In incandescent light, it exhibits a reddish-orange to red color.

The spessartite-grossular-pyrope color-change garnet exhibits a change of color from light bluish green in transmitted fluorescent light to purple in reflected fluorescent light. In incandescent light, the color is light red to purplish red. The refractive index is 1.763 with a specific gravity norm of 3.89.
 

Africa Colored Gemstone Mining
 

Again, the Color Encyclopedia of Gemstones is the source of the information concerning the pyrope-spessartite color-change garnet found in the Umba Valley of East Africa. Calcium and titanium are a part of its chemical composition. A refractive index of 1.757 and a specific gravity of 3.816 are normal. The spectrum exhibits absorption bands at 4100, 4210, and 4300 that may merge to form a cutoff at 4350.  A wide definite band at 5730 occurs in material that exhibits a strong change of color. Acicular rutile and hematite platelets are common inclusions. These gems change from reddish purple in tungsten light to greenish-blue in daylight.
 
Another mixed garnet species material mined at Tunduru gravels in east Africa shows a significant color change, some of the material going from Red to blue or from pink to green colors when going from outdoor to indoor lighting.  Color change garnet comes from Madagascar as well.   Some of the best stones are from the deposit in Bekily, Southern Madagascar.   Stones from this mine are well known for their strong alexandrite-like color change.  This material is quite rare, and usually fairly expensive for a garnet.
 
 
Ceylon
 
 
Ceylon Gemstone Mining
 
 
 
The Ceylon (Sri Lanka) gems change from reddish purple in incandescent to blue, green, gray in daylight.
 
 
Norway
 
Color-change garnet crystals of less than a carat that have been recovered in Norway. The material exhibits a refractive index of 1.747 with a density of 3.715. The color changes from violet in daylight to wine-red in incandescent light. Also found in Norway have been Alexandrite-like garnets with a color change from violet-red to blue-green. He notes only that although they are small, a stone of 24.87 carats was sold in 1979.
 
 
USA
 
Idaho garnets, which are primarily almandine/pyrope mixtures, occasionally show a strong color shift from red to purplish red.
 

Mythology
 
Throughout time, there have been many ancient traditions and legends about the gemstone garnet...

Garnets have been known to Man for thousands of years. Noah, it is said, used a finely cut, glowing garnet within a lantern to help him steer his ark through the dark night.

Many an early explorer and traveler liked to carry a garnet with him, for the garnet was popular as a talisman and protective stone, as it was believed to light up the night and protect its bearer from evil and disaster.

The name “garnet” comes from the Latin word “Garanatus,” meaning “seedlike,” in reference to a pomegranate. This reference makes sense as small garnets look like the bright red seeds you find inside in a pomegranate.

In medieval times, garnets were thought to cure depression, protect against bad dreams, and relieve diseases of the liver, as well as hemorrhages.

Hebrew writers include the garnet as one of the twelve gems in Aaron’s breastplate.

Christian tradition considered the blood-red garnet as a symbol of Christ’s sacrifice.

The Koran holds that the garnet illuminates the Fourth Heaven of the Moslems.

The Greeks said garnet guarded children from drowning. It was also thought to be potent against poisons.

Garnets were found as beads in a necklace worn by a young man in a grave that dates back to 3000 B.C. This is proof of the hardness and durability of the stone.

Plato had his portrait engraved on a garnet by a Roman engraver.

Garnet is the Birthstone for the month of January and the stone that celebrates the 2nd anniversary of marriage.

 

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