INTRODUCTION TO GEMOLOGY
Gemology is the scientific study of gemstones. Although there may be investors and collectors who are only interested in the monetary value of gems, they’ll need a scientific approach when the time comes to distinguish one gemstone from another.
Who will they seek out?
Gemologists.
Reviewing the different types of gemologists and what they do will make a good introduction to gemology, for collectors as well as those curious about careers in Gemology .
Jewelers and Goldsmiths Jewelers need to understand Gemology to answer their customer's questions and identify any gems brought to them.
Goldsmiths (and other metalworkers) need specific knowledge about the physical characteristics of gems in order to create appropriate settings. For example, a setting that would be ideal for a diamond could damage an opal, and the amount of pressure used to set the prongs on a garnet could break a tanzanite Some gems can withstand the heat of repair work involving high temperature soldering and can be left in their settings if precautions are taken. Other gemstones are so heat sensitive they would need to be removed.
Lapidaries Lapidaries, or gem cutters, also need special knowledge. Appropriate cutting and polishing techniques vary from gem to gem. What would work well for one gemstone would be a waste of time or even disastrous on another gem. Faceting and gemstone color management go hand in hand. How the rough is oriented can greatly impact the appearance of the finished gem. Cutting style is also a part of color management.
The choice of cut can lighten or darken a gem, which will considerably affect both the appearance and the value of the stone. The shape, number, and location of facets influence the brilliance of the gem. The angles at which the facets are cut must be carefully chosen. All these factors must be considered to minimize the amount of gemstone rough sacrificed to create a beautiful faceted gem.
The Scientists Although scientists with degrees in geology, chemistry, and even physics make up the smallest group of gemologists, they are influential. The systematic measurement and recording of the physical and optical properties used to identify gemstones is a well established but ongoing scientific process. For centuries, the lapidary was in the best position to recognize the differences in gems with similar appearances. The faceting process offered a perspective on gemstones no other gemologist had. Many inclusions, materials trapped inside gemstones, and physical characteristics, such as hardness, were readily apparent when cutting and polishing a gem. Scientists continue to add to this knowledge by developing new testing techniques and researching new gemstones discovered in nature and synthesized in the laboratory.
Gemstone Identification Gem identification is the heart of gemology. For example, some rubies and garnets are impossible to distinguish by observation, but their physical properties differ considerably. Ruby and garnet crystallography varies greatly. While the visible shapes of individual stones may vary, the crystal structures of these gems at the atomic level are distinctive. Garnets form in the cubic system. Rubies form in the hexagonal system.
Mineralogical techniques are also used to help identify gemstones. Scratch tests, in which various substances are used to scratch an unknown gem, determine hardness. A gem’s reaction to acid and even heat can yield important clues to its identity. Of course, these destructive tests are not appropriate for cut gems.
Scientists have also devised non-destructive tests to identify gemstones. Instruments were designed to measure the physical and optical properties of gems without damaging them. Today, even people without extensive scientific training or expensive laboratory equipment can use these methods for gem identification.
Getting Started in Gemology If you’re interested in learning about gems, the first step is to learn how they’re categorized and the terms used to describe them. Next, study their physical and optical properties. With this background, you can start learning how to identify gemstones.
Of course, there are many side roads to travel as you study gemology. You might become fascinated with phenomenal gems or with inclusions found in natural gems. People interested in gemstone collecting may also become interested in learning how to cut gems and make jewelry. Whether your interest is casual or professional, the world of gemstones will amaze you. You can explore it from your desk or get your hands dirty at a dig!
This is just a brief introduction to gemology. If you want to pursue gemology seriously, the International Gem Society offers an internet-based gemology certification program.
wiki
Background Rudimentary education in gemology for jewelers and gemologists began in the nineteenth century, but the first qualifications were instigated after the National Association of Goldsmiths of Great Britain (NAG) set up a Gemmological Committee for this purpose in 1908. This committee matured into the Gemmological Association of Great Britain (also known as Gem-A), now an educational charity and accredited awarding body with its courses taught worldwide. The first US graduate of Gem-A's Diploma Course, in 1929, was Robert Shipley, who later established both the Gemological Institute of America and the American Gem Society. There are now several professional schools and associations of gemologists and certification programs around the world.
The first gemological laboratory serving the jewelry trade was established in London in 1925, prompted by the influx of the newly developed "cultured pearl" and advances in the synthesis of rubies and sapphires. There are now numerous gem labs around the world requiring ever more advanced equipment and experience to identify the new challenges - such as treatments to gems, new synthetics and other new materials.
Gemmological travel lab KA52KRS It is often difficult to obtain an expert judgement from a neutral laboratory. Analysis and estimation in the gemstone trade usually have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which pool all necessary instruments in a travel case. Such so-called travel labs even have their own current supply, which makes them independent from infrastructure. They are also suitable for gemological expeditions.
Gemstones are basically categorized based on their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism. The physical property of "hardness" is defined by the non-linear Mohs scale of mineral hardness.
Gemologists study these factors while valuing or appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural fluid inclusions or partially melted exogenous crystals that are evidence of heat treatment to enhance color.
The spectroscopic analysis of cut gemstones also allows a gemologist to understand the atomic structure and identify its origin, which is a major factor in valuing a gemstone. For example, a ruby from Burma will have definite internal and optical activity variance from a Thai ruby.
When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal characteristics under magnification.
General identification of gems Gem identification is basically a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity. Any single test is indicative, only. For example, the specific gravity of ruby is 4.00, glass is 3.15–4.20, and cubic zirconia is 5.6–5.9. So one can easily tell the difference between cubic zirconia and the other two; however, there is overlap between ruby and glass.
And, as with all naturally occurring materials, no two gems are identical. The geological environment they are created in influences the overall process so that although the basics can be identified, the presence of chemical "impurities" and substitutions along with structural imperfections create "individuals".
Identification by refractive index Traditional handheld refractometer One test to determine the gem's identity is to measure the refraction of light in the gem. Every material has a critical angle, above which point light is reflected back internally. This can be measured and thus used to determine the gem's identity. Typically this is measured using a refractometer, although it is possible to measure it using a microscope.
Identification by specific gravity Specific gravity, also known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones.
Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
Identification by spectroscopy This method uses a similar principle to how a prism works to separate white light into its component colors. A gemological spectroscope is employed to analyze the selective absorption of light in the gem material. Essentially, when light passes from one medium to another, it bends. Blue light bends more than red light. How much the light bends will vary depending on the gem material. Coloring agents or chromophores show bands in the spectroscope and indicate which element is responsible for the gem's color.
Who will they seek out?
Gemologists.
Reviewing the different types of gemologists and what they do will make a good introduction to gemology, for collectors as well as those curious about careers in Gemology .
Jewelers and Goldsmiths Jewelers need to understand Gemology to answer their customer's questions and identify any gems brought to them.
Goldsmiths (and other metalworkers) need specific knowledge about the physical characteristics of gems in order to create appropriate settings. For example, a setting that would be ideal for a diamond could damage an opal, and the amount of pressure used to set the prongs on a garnet could break a tanzanite Some gems can withstand the heat of repair work involving high temperature soldering and can be left in their settings if precautions are taken. Other gemstones are so heat sensitive they would need to be removed.
Lapidaries Lapidaries, or gem cutters, also need special knowledge. Appropriate cutting and polishing techniques vary from gem to gem. What would work well for one gemstone would be a waste of time or even disastrous on another gem. Faceting and gemstone color management go hand in hand. How the rough is oriented can greatly impact the appearance of the finished gem. Cutting style is also a part of color management.
The choice of cut can lighten or darken a gem, which will considerably affect both the appearance and the value of the stone. The shape, number, and location of facets influence the brilliance of the gem. The angles at which the facets are cut must be carefully chosen. All these factors must be considered to minimize the amount of gemstone rough sacrificed to create a beautiful faceted gem.
The Scientists Although scientists with degrees in geology, chemistry, and even physics make up the smallest group of gemologists, they are influential. The systematic measurement and recording of the physical and optical properties used to identify gemstones is a well established but ongoing scientific process. For centuries, the lapidary was in the best position to recognize the differences in gems with similar appearances. The faceting process offered a perspective on gemstones no other gemologist had. Many inclusions, materials trapped inside gemstones, and physical characteristics, such as hardness, were readily apparent when cutting and polishing a gem. Scientists continue to add to this knowledge by developing new testing techniques and researching new gemstones discovered in nature and synthesized in the laboratory.
Gemstone Identification Gem identification is the heart of gemology. For example, some rubies and garnets are impossible to distinguish by observation, but their physical properties differ considerably. Ruby and garnet crystallography varies greatly. While the visible shapes of individual stones may vary, the crystal structures of these gems at the atomic level are distinctive. Garnets form in the cubic system. Rubies form in the hexagonal system.
Mineralogical techniques are also used to help identify gemstones. Scratch tests, in which various substances are used to scratch an unknown gem, determine hardness. A gem’s reaction to acid and even heat can yield important clues to its identity. Of course, these destructive tests are not appropriate for cut gems.
Scientists have also devised non-destructive tests to identify gemstones. Instruments were designed to measure the physical and optical properties of gems without damaging them. Today, even people without extensive scientific training or expensive laboratory equipment can use these methods for gem identification.
Getting Started in Gemology If you’re interested in learning about gems, the first step is to learn how they’re categorized and the terms used to describe them. Next, study their physical and optical properties. With this background, you can start learning how to identify gemstones.
Of course, there are many side roads to travel as you study gemology. You might become fascinated with phenomenal gems or with inclusions found in natural gems. People interested in gemstone collecting may also become interested in learning how to cut gems and make jewelry. Whether your interest is casual or professional, the world of gemstones will amaze you. You can explore it from your desk or get your hands dirty at a dig!
This is just a brief introduction to gemology. If you want to pursue gemology seriously, the International Gem Society offers an internet-based gemology certification program.
wiki
Background Rudimentary education in gemology for jewelers and gemologists began in the nineteenth century, but the first qualifications were instigated after the National Association of Goldsmiths of Great Britain (NAG) set up a Gemmological Committee for this purpose in 1908. This committee matured into the Gemmological Association of Great Britain (also known as Gem-A), now an educational charity and accredited awarding body with its courses taught worldwide. The first US graduate of Gem-A's Diploma Course, in 1929, was Robert Shipley, who later established both the Gemological Institute of America and the American Gem Society. There are now several professional schools and associations of gemologists and certification programs around the world.
The first gemological laboratory serving the jewelry trade was established in London in 1925, prompted by the influx of the newly developed "cultured pearl" and advances in the synthesis of rubies and sapphires. There are now numerous gem labs around the world requiring ever more advanced equipment and experience to identify the new challenges - such as treatments to gems, new synthetics and other new materials.
Gemmological travel lab KA52KRS It is often difficult to obtain an expert judgement from a neutral laboratory. Analysis and estimation in the gemstone trade usually have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which pool all necessary instruments in a travel case. Such so-called travel labs even have their own current supply, which makes them independent from infrastructure. They are also suitable for gemological expeditions.
Gemstones are basically categorized based on their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism. The physical property of "hardness" is defined by the non-linear Mohs scale of mineral hardness.
Gemologists study these factors while valuing or appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural fluid inclusions or partially melted exogenous crystals that are evidence of heat treatment to enhance color.
The spectroscopic analysis of cut gemstones also allows a gemologist to understand the atomic structure and identify its origin, which is a major factor in valuing a gemstone. For example, a ruby from Burma will have definite internal and optical activity variance from a Thai ruby.
When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal characteristics under magnification.
General identification of gems Gem identification is basically a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity. Any single test is indicative, only. For example, the specific gravity of ruby is 4.00, glass is 3.15–4.20, and cubic zirconia is 5.6–5.9. So one can easily tell the difference between cubic zirconia and the other two; however, there is overlap between ruby and glass.
And, as with all naturally occurring materials, no two gems are identical. The geological environment they are created in influences the overall process so that although the basics can be identified, the presence of chemical "impurities" and substitutions along with structural imperfections create "individuals".
Identification by refractive index Traditional handheld refractometer One test to determine the gem's identity is to measure the refraction of light in the gem. Every material has a critical angle, above which point light is reflected back internally. This can be measured and thus used to determine the gem's identity. Typically this is measured using a refractometer, although it is possible to measure it using a microscope.
Identification by specific gravity Specific gravity, also known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones.
Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
Identification by spectroscopy This method uses a similar principle to how a prism works to separate white light into its component colors. A gemological spectroscope is employed to analyze the selective absorption of light in the gem material. Essentially, when light passes from one medium to another, it bends. Blue light bends more than red light. How much the light bends will vary depending on the gem material. Coloring agents or chromophores show bands in the spectroscope and indicate which element is responsible for the gem's color.