seax hilt fitting – gold with gemstone inlay of
garnet cloisonné. From the
Staffordshire Hoard, found in 2009, and not fully cleaned , a rare bright-green garnet
Gemstones Red garnets were the most commonly used gemstones in the
Late Antique Roman world, and the
Migration Period art of the "
barbarian" peoples who took over the territory of the
Western Roman Empire. They were especially used inlaid in gold cells in the
cloisonné technique, a style often just called garnet cloisonné, found from
Anglo-Saxon England, as at
Sutton Hoo, to the
Black Sea. Thousands of Tamraparniyan gold, silver and red garnet shipments were made in the
Old World, including to Rome, Greece, the Middle East,
Serica and Anglo Saxons; recent findings such as the
Staffordshire Hoard and the pendant of the
Winfarthing Woman skeleton of
Norfolk confirm an established gem trade route with
South India and
Tamraparni (ancient
Sri Lanka), known from antiquity for its production of gemstones. Pure crystals of garnet are still used as gemstones. The gemstone varieties occur in shades of green, red, yellow, and orange. In the United States it is known as the
birthstone for January. It is also the birthstone of
Aquarius and
Capricorn in
tropical astrology. The garnet family is one of the most complex in the gem world. It is not a single species, but is composed of multiple species and varieties.
Almandine garnet is the state mineral of
Connecticut, star garnet is the state gemstone of
Idaho, garnet is the state gemstone of
New York, and
grossular garnet is the state gemstone of
Vermont.
Industrial uses Garnet sand is a good
abrasive, and a common replacement for silica sand in abrasive blasting operations. Alluvial garnet grains which are rounder are more suitable for such blasting treatments. Mixed with very high pressure water, garnet is used to cut
steel and other materials in
water jets. For water jet cutting, garnet extracted from hard rock is suitable since it is more angular in form, therefore more efficient in cutting. Garnet paper is favored by cabinetmakers for finishing bare wood. Garnet sand is also used for
water filtration media. As an abrasive, garnet can be broadly divided into two categories; blasting grade and water jet grade. The garnet, as it is mined and collected, is crushed to finer grains; all pieces which are larger than 60
mesh (250 micrometers) are normally used for sand blasting. The pieces between 60 mesh (250 micrometers) and 200 mesh (74 micrometers) are normally used for water jet cutting. The remaining garnet pieces that are finer than 200 mesh (74 micrometers) are used for glass polishing and lapping. Regardless of the application, the larger grain sizes are used for faster work and the smaller ones are used for finer finishes. There are different kinds of abrasive garnets which can be divided based on their origin. The largest source of abrasive garnet today is garnet-rich beach sand which is quite abundant on
Indian and
Australian coasts and the main producers today are Australia and India. This material is particularly popular due to its consistent supplies, huge quantities and clean material. The common problems with this material are the presence of ilmenite and chloride compounds. Since the material has been naturally crushed and ground on the beaches for past centuries, the material is normally available in fine sizes only. Most of the garnet at the
Tuticorin beach in south India is 80 mesh, and ranges from 56 mesh to 100 mesh size.
River garnet is particularly abundant in Australia. The river sand garnet occurs as a
placer deposit.
Rock garnet is perhaps the garnet type used for the longest period of time. This type of garnet is produced in America, China and western India. These crystals are crushed in mills and then purified by wind blowing, magnetic separation, sieving and, if required, washing. Being freshly crushed, this garnet has the sharpest edges and therefore performs far better than other kinds of garnet. Both the river and the beach garnet suffer from the tumbling effect of hundreds of thousands of years which rounds off the edges.
Gore Mountain Garnet from
Warren County, New York, USA, is a significant source of rock garnet for use as an industrial abrasive. ==See also==