What are Garnets Used for?
With their deep red color and enduring hardness, garnets have been valued for both their beauty and their practical nature for centuries. Legend holds that Noah used a garnet lantern in the bow of the ark to guide him through the night. Deep red garnets were prized in Victorian jewelry and were believed to protect their wearer from nightmares. Found in Africa, Brazil, India, Madagascar, Canada and the United States, garnets have many decorative and industrial uses.
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What Are Garnets?
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Garnet actually refers to a group of minerals that are similar in their composition and properties. Composed of silica and one of several metal molecules, garnets don't cleave like diamonds and other faceted jewels. Instead, when broken they fracture sharply. Garnets are very hard, from 6 to 7.5 on Moh's hardness scale, compared to 10 for diamonds and 3 for calcite. This hardness, and the sharpness of crushed garnet, makes it ideal for many industrial purposes.
The name garnet comes from the Latin word "granatium," which means pomegranate. Deep red garnets were thought to resemble pomegranate seeds. At some point, the "r" and "a" in granat were transposed, and the stones became known as garnets.
Varieties
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The size and quality of garnet determine how it is used. Only the largest, most perfect specimens go into jewelry.
Almandite or almandine ranges in color from black to dark red to orange to brown. The color comes from magnesium and iron in the molecules. Andradite draws its yellow, green and brown coloration from calcium and iron. Andradites are rare and valuable, prized for their luster and a favorite with jewelers.
Grossular are usually red, yellow or orange and may even be clear. They also contain calcium and iron. Some grossular garnets are a deep green, resembling jade and are known as African jade. They are sometimes carved into animals, flowers or decorative figures.
Pyrope garnets are deep red to black due to the presence of chrome. The name rhodolite comes from the Greek word for rose, "rhodo," which refers to the stone's lovely pink color. The pink may range from pale to almost purple. Rhodolites are among the most expensive and prized garnets for jewelry.
Spessartite is brownish red, caused by iron impurities. It's rare and quite valuable. Uvarorite is a green garnet. Usually small, uvarorite is generally used for industrial purposes rather than in jewelry.
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Sanding and Polishing
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The majority of garnets today are used as industrial abrasives. Garnet is crushed, then graded by size. Garnets are made into sandpaper, sanding belts, discs and strips. Garnet particles are used to polish wood and glass, especially optical glass.
Garnets are also used in abrasive powders and as the abrasive mixed with water and blasted through a jet. Unlike sand or silica, which were previously used in water and sand blasting, garnet doesn't break down during these processes, so can be recycled to be used over and over.
Other Industrial Uses
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Garnet particles are mixed with water and fired in a high-speed jet in a process known as water jet cutting. Water jet cutting slices through metal and even granite with precision and with less dust and noise than other cutting methods.
Because garnet is inert and resists chemical degradation, it's also used in water filtration. Garnet is also used in semiconductor manufacturing.
Jewelry
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Garnet is the birthstone for January. Considered a semiprecious stone, garnets occur in every color but blue, but are most associated with a deep red color. Color variations are caused by impurities in the mineral. Garnets vary in degree of transparency. Garnets can be hard to distinguish from rubies with the naked eye, as they share similar properties.
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References
Resources
- Photo Credit Photo by Jarno http://www.flickr.com/photos/jaja_1985/167345135/
