A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral A mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific chemical composition. Minerals range in composition, which—when cut and polished—is used to make jewelry Jewellery (pronounced /ˈdʒuːəlri/ or /ˈdʒuːələri/ ) or jewelry is an item of personal adornment, such as a necklace, ring, brooch or bracelet, that is worn by a person. It may be made from gemstones or precious metals, but may be from any other material, and may be appreciated because of geometric or other patterns, or meaningful symbols or other adornments.^[1] However certain rocks In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids, (such as lapis-lazuli Lapis lazuli (pronounced /ˈlæpɪs ˈlæzʊlaɪ/ or /ˈlæzjʊli/ LAP-iss LAZ-yu-lye/lee) (sometimes abbreviated to lapis) is a relatively rare, semi-precious stone that has been prized since antiquity for its intense blue color) and organic Organic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon and materials (such as amber Amber is fossil tree resin, which is appreciated for its color and beauty. Good quality amber is used for the manufacture of ornamental objects and jewelry. Although not mineralized, it is often classified as a gemstone or jet Jet is a geological material and is considered to be a minor gemstone. Jet is not considered a true mineral, but rather a mineraloid as it has an organic origin, being derived from decaying wood under extreme pressure) are not minerals, but are still used for jewelry, and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their lustre Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. For example, a diamond is said to have an adamantine lustre and pyrite is said to have a metallic lustre. The term is also used to describe other items with a particular sheen (for example, fabric, especially silk and satin, or metals) or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.

Characteristics and classification

Gemstones are identified by gemologists Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems, who describe gems and their characteristics using technical terminology Technical terminology is the specialized vocabulary of a field, the nomenclature. These terms have specific definitions within the field, which is not necessarily the same as their meaning in common use. Jargon is similar, but more informal in definition and use, while legal terms of art or words of art have meanings that are strictly defined by specific to the field of gemology Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems. The first characteristic a gemologist Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems uses to identify a gemstone is its chemical composition In chemistry, the empirical formula of a chemical compound is a simple expression of the relative numbers of each type of atom in it, or the simplest whole number ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as. For example, diamonds In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face centered cubic crystal structure called a diamond lattice. Diamond is the second most stable form of carbon after graphite; however, the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is are made of carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of (C) and rubies A ruby is a pink to blood-red gemstone, a variety of the mineral corundum . The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, of aluminium Aluminium ( ˌæljʊˈmɪniəm ) or aluminum ( /əˈluːmɪnəm/ (help·info), see spelling below) is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances. Aluminium is the most abundant metal in the Earth's crust, and the oxide (Al₂O₃). Next, many gems are crystals which are classified by their crystal system A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups. A major application is in crystallography, to categorize crystals, but by itself the topic is one of 3D Euclidean geometry such as cubic The cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals or trigonal In crystallography, the rhombohedral crystal system is one of the seven lattice point groups, named after the two-dimensional rhombus. A crystal system is described by three basis vectors. In the rhombohedral system, the crystal is described by vectors of equal length, none of which are orthogonal. The rhombohedral system can be thought of as the or monoclinic In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a parallelogram as its base. Hence two pairs of vectors are. Another term used is habit The many terms used by mineralogists to describe crystal habits are useful in communicating what specimens of a particular mineral often look like. Recognizing numerous habits helps a mineralogist to identify a large number of minerals. Some habits are distinctive of certain minerals, although most minerals exhibit many differing habits . Crystal, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.

Gemstones are classified into different groups, species, and varieties. For example, ruby A ruby is a pink to blood-red gemstone, a variety of the mineral corundum . The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, is the red variety of the species corundum Corundum is a crystalline form of aluminium oxide and is one of the rock-forming minerals. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red, while all other colors are called sapphire, while any other color of corundum is considered sapphire Sapphire refers to gem varieties of the mineral corundum, an aluminium oxide (α-Al2O3), when it is a color other than red, in which case the gem would instead be a ruby. Trace amounts of other elements such as iron, titanium, or chromium can give corundum blue, yellow, pink, purple, orange, or greenish color. Pink-orange corundum are also. Emerald Emeralds are a variety of the mineral beryl (Be3Al26,) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of mineral hardness. Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. The word "emerald" (green), aquamarine (blue), bixbite The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white. The (red), goshenite (colorless), heliodor The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Beryl exhibits conchoidal fracture, has a hardness of 7.5–8, and a specific gravity of 2.63–2.80. It has a vitreous luster and (yellow), and morganite The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white. The (pink) are all varieties of the mineral species beryl The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white. The.

Gems are characterized in terms of refractive index The refractive index of a medium is a measure of how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical soda-lime glass has a refractive index of 1.5, which means that in glass, light travels at 1 / 1.5 = 0.67 times the speed of light in a vacuum. Two common properties of glass and other, dispersion In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency. Media having such a property are termed dispersive media. Dispersion is sometimes called chromatic dispersion to emphasize its wavelength-dependent nature, or group-velocity, specific gravity Specific gravity is defined as the ratio of the density of a given solid or liquid substance to the density of water at a specific temperature and pressure, typically at 4 °C and 1 atm (760.00 mmHg), hardness The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science. The method, however, is of great antiquity, having, cleavage Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye, fracture The word fracture is often applied to bones of living creatures, or to crystals or crystalline materials, such as gemstones or metal. Sometimes, in crystalline materials, individual crystals fracture without the body actually separating into two or more pieces. Depending on the substance which is fractured, a fracture reduces strength or inhibits, and luster Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. For example, a diamond is said to have an adamantine lustre and pyrite is said to have a metallic lustre. The term is also used to describe other items with a particular sheen (for example, fabric, especially silk and satin, or metals). They may exhibit pleochroism Pleochroism is caused by the double refraction of light by a mineral. Light of different polarizations is bent different amounts by the crystal, and therefore follows different paths through the crystal. The components of a divided light beam follow different paths within the mineral and travel at different speeds, and each path will absorb or double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain types of material, such as calcite crystals or boron nitride, depending on the polarization of the light. This effect can occur only if the structure of the material is anisotropic (directionally dependent). If the material has. They may have luminescence Luminescence is light that usually occurs at low temperatures, and is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light generated by high temperatures. Historically, radioactivity was thought of and a distinctive absorption spectrum A material's absorption spectrum shows the fraction of incident electromagnetic radiation absorbed by the material over a range of frequencies. An absorption spectrum is, in a sense, the opposite of an emission spectrum. Every chemical element has absorption lines at several particular wavelengths corresponding to the differences between the.

Material or flaws within a stone may be present as inclusions Inclusions are usually other minerals or rocks, but may also be water, gas or petroleum. Liquid or vapor inclusions are known as fluid inclusions. In the case of amber it is possible to find insects and plants as inclusions.

Value of gemstones

There are no universally accepted grading systems for any gemstone other than white (colorless) diamond. Diamonds are graded using a system developed by the Gemological Institute of America The Gemological Institute of America, or GIA, is a non-profit institute dedicated to research and education in the field of gemology. GIA is also well known for its gem identification and grading services, and developed the famous "four Cs" methodology of grading diamonds. Although GIA is best known for its activities in relation to (GIA) in the early 1950s. Historically all gemstones were graded using the naked eye. The GIA system included a major innovation, the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision).^[2]

For the past several hundred years, gemstones have been broken down into two categories; precious and semi-precious. Though today we think primarily of diamond, ruby, sapphire, and emerald as "precious", these categories are based mainly on fashion and the composition of these two lists has changed frequently over time.^[3]

A mnemonic device A mnemonic device is a memory and/or learning aid. Commonly met mnemonics are often verbal, something such as a very short poem or a special word used to help a person remember something, particularly lists, but may be visual, kinesthetic or auditory. Mnemonics rely on associations between easy-to-remember constructs which can be related back to, the "four C's" (color, cut, clarity and carat), has been introduced to help the consumer understand the factors used to grade a diamond.^[4] With modification these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamond. In diamonds, cut is the primary determinant of value followed by clarity and color. Diamonds are meant to sparkle, to break down light into its constituent rainbow colors (dispersion) chop it up into bright little pieces (scintillation) and deliver it to the eye (brilliance). In its rough crystalline form, a diamond will do none of these things, it requires proper fashioning and this is called "cut". In gemstones that have color, including colored diamonds, it is the purity and beauty of that color that is the primary determinant of quality.

Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have a number of inclusions), cut, unusual optical phenomena An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics. A Mirage is an example of an optical phenomenon within the stone such as color zoning, and asteria Asteria, or star stone is a name applied to ornamental stones that exhibit a luminous star when cut en cabochon. The typical asteria is the star-sapphire, generally a bluish-grey corundum, milky or opalescent, with a star of six rays. In red corundum the stellate reflexion is less common, and hence the star-ruby occasionally found with the star- (star effects). The Greeks for example greatly valued asteria in gemstones, which were regarded as a powerful love charm, and Helen of Troy was known to have worn star-corundum Corundum is a crystalline form of aluminium oxide and is one of the rock-forming minerals. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red, while all other colors are called sapphire.^[5]

A factor in determining the value of a gemstone is called water. Water is an archaic term that refers to the combination of color and transparency in gemstones; used hierarchically: first water (gem of the finest water), second water, third water, byewater.^[6]

Historically gemstones were classified into precious stones and semi-precious stones. Because such a definition can change over time and vary with culture, it has always been a difficult matter to determine what constitutes precious stones.^[7]

Aside from the diamond In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face centered cubic crystal structure called a diamond lattice. Diamond is the second most stable form of carbon after graphite; however, the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is, the ruby A ruby is a pink to blood-red gemstone, a variety of the mineral corundum . The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald,, sapphire, emerald, pearl (strictly speaking not a gemstone) and opal ^[7] have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine, peridot and cat's eye have been popular and hence been regarded as precious.

Nowadays such a distinction is no longer made by the trade. ^[6] Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments etc. Nevertheless, diamonds, rubies, sapphires and emeralds still have a reputation that exceeds those of other gemstones.

Rare or unusual gemstones, generally meant to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and bixbite.

Gems prices can fluctuate heavily (such as those of tanzanite over the years) or can be quite stable (such as those of diamonds). In general per carat prices of larger stones are higher than those of smaller stones, but popularity of certain sizes of stone can affect prices. Typically prices can range from 1USD/carat for a normal amethyst to 20,000-50,000USD for a collector's three carat pigeon-blood almost "perfect" ruby.

Grading

In the last two decades there has been a proliferation of certification for gemstones. There are a number of ^[6] laboratories which grade and provide reports on diamonds. As there is no universally accepted grading system for colored gemstones, only one laboratory, AGL (see below) grades gemstones for quality using a proprietary system developed by the lab.

• International Gemological Institute (IGI), independent laboratory for grading and evaluation of diamonds, jewellery and colored stones.
• Gemological Institute of America (GIA), the main provider of education services and diamond grading reports
• American Gemological Society (AGS) is not as widely recognized nor as old as the GIA.
• American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA) a trade organization of jewelers and dealers of colored stones.
• American Gemological Laboratories (AGL) which has been taken over by "Collector's Universe" a NASDAQ listed company which specializes in certification of collectables such as coins and stamps
• European Gemological Laboratory (EGL).
• Gemological Association of All Japan (GAAJ), aka Zenhokyo, Japan, active in gemological research
• Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University
• Asian Institute of Gemmological Sciences (AIGS), the oldest gemological institute in South East Asia, involved in gemological education and gem testing
• Swiss Gemmological Institute (SSEF), founded by Prof. Henry Hänni, focusing on coloured gemstones and the identification of natural pearls
• Gübelin Gem Lab, the traditional Swiss lab founded by the famous Dr. Eduard Gübelin. Their reports are widely considered as the ultimate judgement on high-end pearls, coloured gemstones and diamonds

Each laboratory has its own methodology to evaluate gemstones. Consequently a stone can be called "pink" by one lab while another lab calls it "Padparadscha". One lab can conclude a stone is untreated, while another lab concludes that it is heat treated ^[6]. To minimise such differences, seven of the most respected labs, i.e. AGTA-GTL (New York), CISGEM (Milano), GAAJ (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), aiming at the standardisation of wording on reports and certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to find agreement on due to the constant discovery of new locations. Moreover determining a "country of origin" is much more difficult than determining other aspects of a gem (such as cut, clarity etc.) ^[8].

Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate ^[6].

Cutting and polishing

A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.

Stones which are opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones.^[9]

Gems which are transparent are normally faceted, a method which shows the optical properties of the stone’s interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones. The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. The faceting machine is used to hold the stone onto a flat lap for cutting and polishing the flat facets.^[10] Rarely, some cutters use special curved laps to cut and polish curved facets.

Gemstone color

Color is the most obvious and attractive feature of gemstones. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colors of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light - blue, yellow, green, etc. - except red.

The same material can exhibit different colors. For example ruby and sapphire have the same chemical composition (both are corundum) but exhibit different colors. Even the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".

This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom (and this could be as few as one in a million atoms). These so called impurities are sufficient to absorb certain colors and leave the other colors unaffected.

As an example: beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.

Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem.

Treatments applied to gemstones

Gemstones are often treated to enhance the color or clarity of the stone. Depending on the type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone.^[11]

Heat

Heat can improve gemstone color or clarity. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in ametrine - a stone partly amethyst and partly citrine. Much aquamarine is heat treated to remove yellow tones, change the green color into the more desirable blue or enhance its existing blue color to a purer blue. ^[12]

Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more desirable blue/purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity.

When jewelry containing diamonds is heated (for repairs) the diamond should be protected with boracic acid; otherwise the diamond (which is pure carbon) could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies is heated (for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.

Radiation

Most blue topaz, both the lighter and the darker blue shades such as "London" blue, has been irradiated to change the color from white to blue. Some improperly handled gems which do not pass through normal legal channels may have a slight residual radiation^{[citation needed]}, though strong requirements on imported stones are in place to ensure public safety. Most greened quartz (Oro Verde) is also irradiated to achieve the yellow-green color.

Waxing/oiling

Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner.

Fracture filling

Fracture filling has been in use with different gemstones such as diamonds, emeralds and sapphires. In 2006 "glass filled rubies" received publicity. Rubies over 10 carat (2 g) with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect.

Synthetic and artificial gemstones

Some gemstones are manufactured to imitate other gemstones. For example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. Moissanite is another example. The imitations copy the look and color of the real stone but possess neither their chemical nor physical characteristics.

However, lab created gemstones are not imitations. For example, diamonds, ruby, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics to the naturally occurring variety. Synthetic (lab created) corundums, including ruby and sapphire, are very common and they cost only a fraction of the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives. Larger synthetic diamonds of gemstone quality, especially of the colored variety, are also manufactured.^{[citation needed]}

Whether a gemstone is a natural stone or a lab-created (synthetic) stone, the characteristics of each are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab, so therefore do not affect the clarity or color of the stone. However, natural gemstones are still considered more valuable on average due to their relative scarcity.^{[citation needed]}

Birthstones

The birthstones for each month are:^{[citation needed]}

• January- Garnet
• February- Amethyst
• March- Aquamarine
• April- Diamond
• May- Emerald
• June- Pearl
• July- Ruby
• August- Peridot
• September- Sapphire
• October- Opal
• November- Topaz
• December- Turquoise

See also

• List of famous gemstones
• Lapidary

Notes

1. ^ The Oxford Dictionary Online and Webster Online Dictionary
2. ^ Wise, R. W., 2006, Secrets of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, p.36 ISBN 0972822380
3. ^ Wise, R. W., 2006, Secrets Of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, pp.3-8 ISBN 0972822380
4. ^ Wise, R. W., 2006, Secrets Of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, p. 15
5. ^ Burnham, S.M. (1868). Precious Stones in Nature, Art and Literature. Bradlee Whidden. Page 251
6. ^ ^{a b c d e} Secrets of the Gem Trade; The Connoisseur's Guide to Precious Gemstones Richard W Wise, Brunswick House Press, Lenox, Massachutes., 2003
7. ^ ^{a b} Church, A.H. (Professor at Royal Academy of Arts in London) (1905). Precious Stones considered in their scientific and artistic relations. His Majesty's Stationary Office, Wyman & Sons. Chapter 1, Page 9: Definition of Precious Stones URL: Definition of Precious Stones
8. ^ Rapaport report of ICA Gemstone Conferene in Dubai
9. ^ Introduction to Lapidary by Pansy D. Kraus
10. ^ Faceting For Amateurs by Glen and Martha Vargas
11. ^ Gemstone Enhancement: History, Science and State of the Art by Kurt Nassau
12. ^ Nassau, Kurt (1994). Gem Enhancements. Butterworth Heineman.

External links

• History of Gems, Gemology and Mining Library Most of the books used as reference are found online here. (Theophrastus, Church, Williams, George Frederick Kunz etc.)

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