Garnets are a type of mineral deposit with a crystal structure that is abundant throughout the world. Only a few types of garnet are gem quality, however. Other types of garnets are used as industrial abrasives to sand and polish. Garnet has been used as a gemstone from early Greek, Roman and Egyptian times and can come in red, green, yellow and orange hues. Garnet is the birthstone for the month of January.
Garnet Structures
When miners extract garnet crystals from the earth, the garnets may be quite large and well-formed in dodecahedral (12-sided polyhedron) or trapezohedral (24-sided polyhedron) shapes. They can also form in small clusters of crystals that are stuck together. Garnets appear in every color except blue. Jewelers can cut them into faceted gems or rounded cabochons.
Where Garnets Form
Garnet forms in metamorphic rock, that is, previously formed rock that has been subjected to temperature and pressure forces within the Earth. It also forms from chemical reaction in fluids. One can find garnet deposits throughout the world, in the United States, Brazil, Germany, the Czech Republic, Austria, Kenya, Madagascar, Tanzania, Russia, Pakistan, Sri Lanka, China and India. Any of these formations can include gemstone quality garnets along with lesser quality material.
Mining Garnets
Miners extract garnets in a number of ways. In open pit mining, workers remove the soil from an area, and then chip the rock out of the ground by hand or with machinery. This method can damage agricultural areas, so miners developed another method in which they dig vertical shafts into the ground, supported by timbers. They use pumps to keep the shafts from filling with water. Miners then go into the shafts and cut the garnet out of the veins and carry them to the surface. You can also find garnets in placer mines, areas of low water velocity in rivers, creeks, and natural hollows where the crystals collect naturally and you can remove them by hand.
Processing Garnets
Workers must remove garnets from the surrounding rock, wash, screen and sort them by quality. This happens on the surface above the mines, often with machinery and conveyors built specifically for the purpose.
Using Garnets
Jewelers then cut gem quality garnets into faceted stones for loose sale or setting into jewelry. Processors grind industrial quality garnets into finer particles and then package it as a loose abrasive for water-jet abrasion, or glue it to paper for use as a hand-held abrasive.
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