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