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Article: Gemstone


Definition and Classification of Gemstones

  • Gemstones are mineral crystals used for making jewelry and adornments.
  • They can be precious or semi-precious stones.
  • Some rocks and organic materials are also considered gemstones.
  • Gemstones are valued for their hardness, luster, and rarity.
  • Gemstones are classified as precious or semi-precious based on rarity and quality.
  • The traditional precious stones are emerald, ruby, sapphire, and diamond.
  • Other gemstones are classified by color, translucency, and hardness.
  • The terms precious and semi-precious can be misleading in a commercial context.
  • Gemstones are identified by their chemical composition, crystal system, and habit.
  • Gemstones belong to different species and varieties.
  • For example, ruby is the red variety of the species corundum.
  • Gemstones are characterized by refractive index, dispersion, hardness, and luster.
  • They may exhibit pleochroism, double refraction, and luminescence.
  • Inclusions and flaws may be present within gemstones.
  • Gemstones do not have a universally accepted grading system.
  • Diamonds are graded using a system developed by the Gemological Institute of America.
  • The four Cs (color, cut, clarity, and carats) are used to grade diamonds.
  • The cut is the primary determinant of value in diamonds.
  • The purity and beauty of color are important for colored gemstones.
  • The pearl and opal have been considered precious alongside diamond, ruby, sapphire, and emerald.
  • Aquamarine, peridot, and cat's eye have also been regarded as precious in the past.
  • The distinction between precious and semi-precious gemstones is no longer made in the gemstone trade.
  • Gemstone pricing is influenced by factors such as clarity, rarity, and demand.
  • Diamonds, rubies, sapphires, and emeralds still have a reputation that exceeds other gemstones.

Gemstone Grading and Evaluation

  • Gemological Institute of America (GIA) is the main provider of education services and diamond grading reports.
  • International Gemological Institute (IGI) is an independent laboratory for grading and evaluation of diamonds, jewelry, and colored stones.
  • Hoge Raad Voor Diamant (HRD Antwerp) is one of Europe's oldest laboratories, with its main stakeholder being the Antwerp World Diamond Centre.
  • American Gemological Society (AGS) is a recognized laboratory, although not as widely known as GIA.
  • American Gem Trade Laboratory is part of the American Gem Trade Association (AGTA) and focuses on colored stones.

Gemstone Cutting and Polishing

  • Gemstones are commonly cut and polished for use in jewelry.
  • Cabochons are smooth, dome-shaped stones, while faceted stones have small flat windows called facets.
  • Opaque or semi-opaque gems like opal and turquoise are often cut as cabochons.
  • Transparent gems are faceted to maximize reflected light and sparkle.
  • Different angles must be cut for the facets to ensure proper reflection.

Gemstone Colors and Treatment

  • The color of a gemstone is determined by the nature of light and the wavelengths that are reflected.
  • Impurities in gemstones can cause variations in color.
  • Even gemstones with the same chemical composition can exhibit different colors due to impurities.
  • Beryl, for example, can become emerald with chromium impurities or pink morganite with manganese impurities.
  • Gemstone treatments are often used to enhance their color, clarity, and durability.
  • Some treatments can affect the value of the stone.
  • Heating is a common practice in the gemstone industry.
  • Radiation treatment enables the creation of rare gemstone colors.
  • Waxing/oiling treatment is used to enhance the color and clarity of gemstones.
  • Fracture filling treatment is used to improve the appearance of gemstones with fractures.
  • Bleaching treatment is used to alter the color of gemstones.
  • Gemstone treatments can be followed by dying or impregnation.
  • Synthetic gemstones are created in a laboratory and have the same characteristics as natural stones.
  • Imitation or simulated stones are chemically different but may look similar to natural stones.

Synthetic Gemstone Production Methods and Characteristics

  • Synthetic gemstones share chemical and physical properties with natural gemstones.
  • Microscopy is often used to distinguish slight differences between synthetic and real gemstones.
  • Flame fusion, Czochralski, flux growth, and hydrothermal growth are common methods for producing synthetic gemstones.
  • Synthetic gemstones have characteristic features specific to the growth process.
  • Auguste Verneuil developed the flame-fusion process in 1902.
  • Synthetic gemstone production has a long history of innovation and development.

Gemstone Mentions

Gemstone Data Sources

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