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Article: Garnet


Physical Properties and Crystal Structure of Garnet

  • Garnet species are found in every color, with reddish shades being the most common.
  • Blue garnets are the rarest and were first reported in the 1990s.
  • Garnet species can range from transparent gemstone-quality specimens to opaque varieties used for industrial purposes.
  • The luster of garnet can be vitreous (glass-like) or resinous (amber-like).
  • Garnet can have any diaphaneity, but translucent is common.
  • Garnets have a general formula of (SiO) with divalent cations occupying the site and trivalent cations occupying the site.
  • Garnets are most often found in the dodecahedral crystal habit, but can also be found in the trapezohedron and hexoctahedral habits.
  • They crystallize in the cubic system, with three axes of equal length perpendicular to each other.
  • Garnets do not have any cleavage planes and fracture into sharp, irregular pieces.
  • The crystal structure of garnet consists of oxygen, silicon, aluminium, and magnesium ions.
  • The hardness of garnet varies depending on its chemical composition.
  • Garnet has a range of hardness on the Mohs scale, from about 6.0 to 7.5.
  • Harder species like almandine are often used for abrasive purposes.
  • The atomic bonds in garnet species can be stronger or weaker, affecting their hardness.
  • Garnet is not easily scratched and is relatively durable.

Identification of Garnet

  • A strong neodymium magnet can be used to separate garnet from other transparent gemstones.
  • Magnetic susceptibility measurements, along with refractive index, can help identify garnet species and determine their composition.
  • This method is commonly used in gem identification in the jewelry trade.
  • Garnets have unique magnetic properties that distinguish them from other gemstones.
  • The response to a magnet can indicate the presence of garnet in a gemstone.

Garnet Group End Member Species

  • Pyralspite garnets include almandine, pyrope, and spessartine.
  • Almandine is an iron-aluminium garnet and is the most common gem garnet.
  • Pyrope is a red garnet with magnesium silicate and can vary in color from deep red to black.
  • Spessartine is a manganese-aluminium garnet and is found in orange-yellow varieties.
  • Ugrandite garnets include andradite, grossular, and uvarovite, which have calcium in their composition.

Industrial Uses and Origin of Garnet

  • Garnet sand is a common replacement for silica sand in sandblasting.
  • Alluvial garnet grains are more suitable for blasting treatments.
  • Garnet is used with high-pressure water to cut steel and other materials in water jets.
  • Garnet paper is favored by cabinetmakers for finishing bare wood.
  • Garnet sand is used for water filtration media.
  • The largest source of abrasive garnet is garnet-rich beach sand found on Indian and Australian coasts.
  • River garnet is particularly abundant in Australia and occurs as a placer deposit.
  • Rock garnet is produced in America, China, and western India.
  • Gore Mountain Garnet from New York, USA, is a significant source of rock garnet.
  • Different kinds of abrasive garnets can be divided based on their origin.

Cultural Significance and Market of Garnet

  • Garnet is the birthstone of January.
  • It is also the birthstone of Aquarius and Capricorn in tropical astrology.
  • In Persia, garnet was considered a talisman from nature's forces.
  • Garnet was believed to signal approaching danger by turning pale.
  • Garnet holds cultural significance in various traditions and beliefs.
  • Garnet is New York State's official gemstone.
  • Connecticut has almandine garnet as its state gemstone.
  • Idaho has star garnet as its state gemstone.
  • Vermont has grossular garnet as its state gemstone.
  • New York State ranks first in industrial garnet production in the United States.
  • The value of garnets depends on factors such as color, clarity, size, and origin.
  • Garnets can range in price from affordable to high-end, depending on their quality and rarity.
  • The market for garnets is influenced by consumer demand, fashion trends, and supply availability.
  • Garnets are traded globally, with major markets in countries like the United States, India, and China.
  • Garnets have cultural and symbolic value in different societies and can be considered a precious gemstone.

Garnet Mentions

Garnet Data Sources

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