Adamantine Refers to the diamond-like luster of a gemstone. Gemstones with a diamond-like luster include diamond (of course), demantoid garnet and sphene.
Adularescence The shimmering light or whitish opalescence which glides over the surface of some gems such as moonstone. Interference phenomena of the layered structure is the cause of this effect.
Alluvial Deposits Gem deposits found in water after they have been separated from the mother rock.
Acicular It is an aggregate of long, slender, crystals i.e. Natrolite. The term is also used for the crystal habit of a single long, thin, slender crystals.
Agate It is a type of chalcedony which is found in many different patterns and colors, often with varying color layers.
Aggregate It is a term given to the grouping of crystals. It is defined by the way crystals are clustered together.
Amethyst Amethyst is a variety from Quartz family, colored by traces of manganese, titanium and iron. Deeper-colored amethysts are more highly valued. It is available in colors like purple, pale lavender to deep reddish purple, bluish violet etc. Rich purple has always been a rare and noble color. Amethyst’s name comes from Greek word 'Amethystos' meaning 'Not Intoxicated' or ‘Not Drunken’. The Amethyst is said to bring good luck and to radiate love. This brilliantly sparkling stone is the most valued gemstone from the quartz family. It is 7 on Mohs hardness scale and mainly found in Kalimantan (Indonesia) and Lampung-Sumatera (Indonesia) with high brilliant sparkling,Sri Lanka, Brazil, Burma, Canada, East Africa, India, North America, Russia, Uruguay, Madagascar and Australia.
Amber The gemstone Amber is the fossilized liquid, resin, or gum from pine trees and available in various colors like golden yellow, golden orange, brown, green, red and violet. These gemstones may contain insects, plant material, feathers and other small objects that were trapped millions of years ago when the resin was sticky. Amber is quite soft but perfect for jewelry as it can be easily cut, etched, faceted, or carved.
Aquamarine It is a semiprecious blue colored stone from the beryl family. It is the birth stone for the month of March.
Artificial stone A look alike gem material which is either a manmade imitation or a synthetic.
Amorphous Gemstones without a crystal structure are referred to as amorphous. These include gems such as amber, coral, opal and pearl.
Asterism The star effect that you see in star sapphires or rubies, for example. This is usually caused by tiny silk rutile inclusions in the stone. The effect can be four- or six- rayed.
Alexandrite Alexandrite is a form of the mineral Chrysoberyl which is a very attractive and rare stone. It is 8.5 on Mohs hardness scale and mainly found in Russia, Sri Lanka, Brazil, Burma, Madagascar and USA. The most sensational feature about this stone is its surprising ability to change its color under different forms of light. Green or bluish-green in daylight, red in candle light, green in fluorescent light and reddish-purple in standard electric (tungsten) light.
Baguette A long rectangular gemstone shape, somewhat similar in shape to a loaf of French bread, hence the name.
Baroque Brilliant Cut A round shaped stone that has a minimum of fifty-eight facets.
Bar Setting In this style of setting, gemstones are individually set between these bars leaving the sides of the stones exposed to light. This method maximizes the amount of light entering the gemstones which create superior brilliance and sparkle.
Bead A hollow gemstone, usually round, designed to be strung.
Bezel Setting In this style of setting, a metal rim gently holds a gemstone in place by the girdle. The bezel setting guards the gemstone from any damages and yet allows light to enter which creates brilliance and sparkle.
Blemish It is a term used to any surface imperfection on the surface of a gemstone. As for example of a diamond, one would be referring to a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish.
Beryl The name beryl comes from ancient Greek word ‘beryllos’ which means precious blue-green color. This stone is available in a variety of colors including green, yellow, greenish-yellow, blue to blue-green, red, colorless and pink.
Beryllium Treatment A form of heat treatment for sapphire that adds the element beryllium to the heating process. Beryllium is an element well known in the gem world, since it is an essential constituent in many gemstones, including emerald, beryl, and aquamarine. When sapphires are heated with beryllium, the result is a reduction in blue tones. Thus bright yellow or orange sapphire can be produced from weak yellow or greenish gems. Some stunning colors have been produced using this method.
Bi-color A gemstone exhibiting two color zones, such as ametrine or many tourmalines.
Birefringence Some gemstones are singly refractive: they have only one refractive index. Other gemstones (in fact, most) are doubly refractive: they have two different refractive indices. When a beam of light enters a doubly refractive gem, it is split into two beams, each travelling at a different speed and on a different path through the crystal. Birefringence is a measurement of the difference between the two refractive indices in gems that are doubly refractive, and it ranges from a low of .003 to a high of .287. Very few gemstones are singly refractive; in fact, the only well-known gems with that property are diamond, spinel and garnet.
Birthstone The association of gemstones with astrology goes back centuries. More recently, jewelers have adapted this tradition to create the current list of official birthstones.
Botryoidal Resembling grape bunches with interlocking rounded masses.Formed from acicular or bladed crystals growing from a common site for each rounded mass. The tops of the crystals are smooth and blend so that individual crystal edges are indiscernible except from broken edges. Botryoidal is similar to globular and mammillary; but more of an aggregation of rounded masses. Sub-botryoidal has more discernible crystals. Chrome Chalcedony,hematite and smithsonite both form aggregates that are good examples of this form.Especially Botryoidal Chrome Chalcedony often found in Indonesia.Botryoidal Chalcedony from Indonesia has known as Grapes Agate or Manakarra Stone. Manakarra Stone is true resembling grape bunches with sparkles,druzy and turtle back inclusions
Brilliance Brilliance describes the reflections of white light returned to the eye from a gemstone. Brilliance is produced primarily when light enters through the table, reaches the pavilion facets, and is then reflected back out through the table. The major factors that affect the amount of brilliancy in a gem are refractive index, proportions, polish and transparency.
Briolette This term is used for a long teardrop shaped gemstone with rose cut facets, which sometimes is also drilled to be used as a pendant.
Cabochon Cut A gem that is cut round without facets into the shape of a smooth polished dome. It lacks the facets that are on most stones.
Calibrated (size) Many gemstones are sold in calibrated or standard sizes that will fit commercial jewelry settings. Standard sizes are calibrated in millimeters for a number of different gem shapes.
Carat A unit of weight for gems. A carat is one fifth of a gram (0.2g).The term Carat is used as a standard unit of measurement of the weight of most gemstones including diamond. The word comes from the carob beans which are known for its consistent weight and was used in ancient times to measure gemstones. One carat (ct.) equals 200 milligrams, or 0.2 grams (1/5 of a gram), or 1/142 of an ounce. There are 100 points in a carat. If all other factors are equal, the more a stone weighs, the more valuable it will be. It is sometimes incorrectly spelled ‘Karat’, but Karat refers only to the fineness of pure gold and gold alloys.
Carbon Spots It is a black-appearing inclusions in diamonds, which is caused by the addition of graphite or homblende minerals.
Carbonates Group It is a group of minerals which contain one or more metallic elements along with the carbonate radical (CO3). Most of them are lightly colored and transparent in pure form. All the carbonates are soft, brittle, and effervesce when they are exposed to warm hydrochloric acid. The carbonates are divided as Calcite group, Aragonite group. Sometimes, the Nitrates and Borates are also considered as a category of the carbonates.
Carlsbad Twin It is form of penetration twinning where the two Orthoclase crystals form interpenetrating twins.
Cassiterite Twin Two crystals which twin in a repeated pattern. It is also known as "repeated twinning."
Cat's Eye See Chatoyancy.
Center Stone The center stone is the prominent center piece in a jewelry setting that has multiple gemstones. See also Side Stone.
Chanthaburi The city in southeastern Thailand famous as one of the world centers for gemstone processing and trading. Chanthaburi is also famous for its weekend gemstone market.
Chatoyancy The cat's eye effect sometimes seen in gemstones such as chrysoberyl, apatite and tourmaline is known by the technical name of chatoyancy. The effect is caused by tiny parallel inclusions that give the appearance of a narrow line similar to a cat's eye. Often a gemstone needs to be viewed in natural light to see the chatoyancy effect.
Chalcedony It is a term which refers to the various types of colored stone, including milky, carnelian, agate, cat's eye and also jasper.
Chrysoberyl Twin It is a form of contact twinning where six Chrysoberyl crystals join at the base to form a six-pointed formation.
Citrine It is a brownish-orange quartz variety. It is the birthstone for the month of November.
Clarity Enhanced It is also sometimes called "fracture filled." It is a term used for a gemstone which has been treated for the improvement of its appearance by filling fissures or fractures with a transparent substance.
Clarity Grade Diamonds are ranked on a scale from flawless, which is no inclusions visible under 10x magnification, to included i.e. eye visible inclusions. Clarity grade is one of the such four value factors.
Clarity Referring to a stone's lack of inclusions or other visual defects.
Cleavage The tendency of crystalline minerals to break in one or more definite directions, producing more or less smooth surfaces. A cleavage may be caused by inherent internal strain or by a sharp blow. Cleavage is one of the two methods used by stone cutters to split gemstones in preparation for the cutting process. The other method is sawing.
Cloud A group of a number of extremely tiny white inclusions which gives a ‘cloudy’ or ‘milky’ appearance under 10X magnification.These clouds cannot be seen with the naked eye and generally does not significantly impact a gemstone's clarity grade.The cloudy inclusions has known as Pandan in Indonesia Community
Color Used in the evaluation of a gem. The quality of a gem can based on either the presence or the absence of color.
Color Change (gemstones) Color change gems change color due to changing light conditions (such as alexandrite or color change sapphire) or when viewed from different angles (such as andalusite or iolite).
Concave Cut Traditional gem facets are flat or two-dimensional. Concave cutting creates facets that are curved or three-dimensional. These curved facets refract more of the ambient light and return it to the eye as brilliance. Concave cutting is a recent innovation dating back to the early 1990s. It requires considerable expertise and results in higher weight loss to the rough stone, since more material must be cut away to create the curved facets.
Copper-Bearing Gemstones that contain traces of copper are very rare and typically have a intense blue, blue-green or violet color. There was considerable excitement in the gem world when the first copper-bearing gemstones were discovered in 1989. See also Paraiba.
Corundum A crystalline form of aluminum oxide known in the gemstone world as ruby and sapphire. It is naturally clear, but can have different colors when impurities are present. Corundum is much admired for its hardness (9.0 on the Mohs scale), brilliance and excellent wearability.
Crystal Structure Crystals are divided in to seven groups on the basis of specific set of angular, geometrical and symmetrical specifications. All crystalline gems can be classified in one of seven groups based on the above specifications. These groups are cubic, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic and triclinic.
Cubic Zirconia A lab created diamond simulant, often abbreviated as CZ. While CZ is a transparent stone, trace elements can be added to the manufacturing process, producing a wide range of colors. On the Mohs scale of hardness, CZ is harder than other gemstones except for diamond, ruby, sapphire and chrysoberyl. Not to be confused with zircon, a natural gemstone.
Culet The lowest part of a gemstone. This looks like the tip or point of the stone.
Cuprian See Copper-bearing.
Demantoid Demantoid is a rare and valuable andradite garnet. It exhibits a range of greens from dull to bright emerald green and on rare occasions displays yellow. On the Mohs scale of hardness, demantoid is relatively soft at 6.5. It has an adamantine luster.
Density The ratio of a gemstone when compared to the weight of an equal volume of water. This means how heavy a gemstone is compared to the same volume of water. Also known as "specific gravity" for solids.
Diamond Cut Also known as the brilliant cut, the style of cutting a stone with multiple facets to maximize brilliance. Modern round brilliant cuts have 58 facets.The word "diamond" comes from the Greek word “Adamas”, meaning "Unconquerable". Diamond is composed of carbon that crystallizes in the “cubic,” or “isometric,” crystal system. It is the hardest known substance in the world (10 on Mohs’ scale). The Diamond is uniquely resistant to damage by heat or scratching, and can be cut or polished only by another diamond. It occurs in colors ranging from colorless to yellow, brown, orange, green, blue, and violet.
Dichoric This term refers to a gemstone that displays a different color or shade, which is other than the original gemstone’s color, when viewed from different directions or angles.
Dispersion Dispersion is the ability of a gemstone, to separate white light into the colors of the spectrum. It is also called the stone’s fire.
Diaphaneity the quality of being diaphanous; transparency
Dichroism A term meaning the ability of some gems to display a second color when viewed from a different angle. A dichroscope can see this change, and is used for identifying certain stones.
Diffusion Treatment A form of heat treatment that adds one or more chemicals to the heating process to change the color of a gemstone. Typically the treatment does not penetrate deep into the stone, so gems treated in this way cannot be recut. Diffusion treatment is a standard treatment to increase the asterism in star sapphire.
Dispersion The separation of light into the seven spectral colors, causing the "fire" of a gemstone, which is refracted by the internal facets. Diamond has a very high dispersion, hence its high amount of "fire".
Double Refraction The ability of most gems to split rays of light into two unequally refracted rays. Also called 'birefringence'.This term is used when each ray of light is split in two as it enters in a non-cubic mineral.
Doublet A doublet is a gemstone composed of valuable gemstone material in combination with other materials. It is found most often in opal, where an opal doublet contains a slice of opal glued to common opal, glass or other material. A triplet contains a slice of opal glued between a base and a crystal or a glass top. Triplets are usually less expensive than doublets, and both are less expensive than natural opals. Doublets may occasionally be found with sapphire or other expensive gemstones.
Eye Clean Refers to a gemstone that appears to have no visible inclusions or imperfections to the naked eye. Compare Loupe Clean.
Emerald Emerald, a variety of mineral Beryl, is one of the most fascinating and beautiful gemstones available in various shades of green color. The name of this remarkable gemstone comes from Greek ‘Smaragdos’, meaning ‘Green Stone’. Deep green is the most desired color in emeralds. Its hardness makes it very tough and durable which comes in between 7.5 to 8 on Mohs hardness scale and it is mainly found in Columbia, Brazil, Zimbabwe, South Africa, Afghanistan and USA. Flawless emeralds are very uncommon, and are noted for their great value, sometimes even more than diamonds.
Emerald Cut Emerald Cut gemstone is a square or rectangular shape stone with cut corners. This is also known as Step Cut because it has rows of facets, usually 48 to 50, that resemble a staircase. Due to its larger, more open table, this shape highlights the clarity of a gemstone but with fewer facets, this shape brings less brilliance than the other shapes.
Enamel Enamel is a powdered colored glass fused onto the surface of the piece of jewelry. It is a soft material and can be easily cracked or damaged. This should not be used on jewelry pieces, which are exposed to daily wear.
Engraving Engraving is a method of surface decoration in which a design is etched or engraved with a sharp tool.
Enhance,Enhanced, Enhancement Enhance or enhancement is the process to improve a gemstone's color or clarity by using various methods like heating and oiling.
Facet The cut and polished flat plane of a gemstone. There can be dozens of facets on a stone.
It is one of the small and flat surfaces of a gemstone which is polished to increase its brilliancy and beauty. A round brilliant cut gemstone has a total of 57 or 58 facets.
Faceted Girdle It is a girdle of a stone which is lapped and polished for its maximum surface reflection. It has many flat planes around the circumference of the stone.
Fancy Cut Sometimes used to refer to a gemstone cut in any shape other than the standard round cut, but also used to refer to gemstones that are cut in a shape other than the well known shapes of round, oval, pear, trillion, marquise, etc.
Feather It is a fracture or break in a gemstone which is typically white and feathery in appearance.
Fire The rainbow of colors that light rays form as they move through a gemstone. This is another word for dispersion.It is the flashes of spectral colors which are seen in a gemstone as a result of dispersion
Fissure A surface crack on a gemstone. Gems with fissures may be fracture filled.
Fluorescence An effect in many gemstones mainly in diamonds that makes them glow in ultraviolet rays or light. Stones can fluoresce in a number of colors mainly in blue. Fluorescence ratings include none, faint, slight, medium, strong and very strong. Faint to medium fluorescence is rarely detected under most lighting conditions which include sunlight also whereas strong or very strong fluorescence may make a stone appear ‘milky’ or ‘oily’ in such lighting conditions. Fluorescence is not dangerous to the stone or to its wearer. It is a unique and fascinating quality that occurs naturally in a number of gems and minerals.
Flaw It is an inclusion or a crack in gemstones which generally demotes its value.
Four C's It is cut, color, clarity, and carat weight. This phrase is used to describe a diamond's value characteristics.
Fracture Filling Small cracks or fissures in a gemstone can interrupt the flow of light through the stone, creating white or "dead" spots in the color of the stone. Sometimes these fractures will be filled with material that will allow the light to pass through smoothly. Different materials are used; oil, wax, glass, epoxy, and borax are common materials. The most commonly filled stones are emerald, turquoise and ruby.
Freshwater Pearl It is term given to a pearl which forms in a freshwater living mollusk.
Full Cut A round-shaped, brilliant-cut gemstone.
Full Cut Diamond It is a description of a brilliant cut, a round stone with 57 to 58 facets.
Garnet Garnet, which belongs to mineral quartz, is a family of stones having many varieties differing in color and in their constituents. This name is derived from its resemblance in color and shape to the seeds of the pomegranate. Garnet Stones are available in varieties named Grossularite, Pyrope, Almandine, Rhodalite, Andradite, Essonite, Tsavorite, Spessartite, Melanite, Allochroite, Ouvarovite and Demantoid. The most common color of Garnets range from light red to violet, but can also be white, green, yellow, brown and black except blue. Its hardness is between 7.5 to 8 on Mohs hardness scale and it is mainly found in Burma, Sri Lanka, South Africa, China, USA, Tanzania, Madagascar, India and Australia.
Garnet Paper It is a sandpaper which is composed of tiny, hard, garnet crystals, glued on it for the use of an abrasive.
Gemology It is the science and procedures being involved in mining, faceting, and also marketing of gemstones.
Gemologist A person with expertise in gemology is known as gemologist. There are many recognized courses available from various Gemological Institutes which offer study in gem identification, grading and pricing.
Gemological Institute of America (GIA) Gemological Institute of America (GIA) was established as a non-profit organization in 1931 by Roger Shipley. GIA maintains the highest standards for grading gemstones and it has one of the world’s most-respected and well-regarded gemological laboratories. GIA has developed and standardize the gemstone grading system that is used by nearly all other gem labs.
Gemstone A gemstone is a mineral or rock, which can be used in jewelry after cutting or faceting and polishing. Gemstones are diverse in their beauty and many gems are available in a stunning variety of colors. Most gemstones have little beauty in the rough state and they may look like ordinary rocks or pebbles in their rough form. After a skilled cutting and polishing of a gem, full color and luster can be seen. Gemstones are classified into two categories, precious and semi-precious, on the basis of their characteristics. Precious stones include diamonds, emeralds, rubies, and sapphires whereas semi precious stones are Alexandrite, Amethyst, Aquamarine, Citrine, Garnet, Iolite, Onyx, Opal, Pearl, Peridot, Tanzanite, Topaz, Tourmaline etc.
Geode Geode is a cavity within a rock which is a crystal line. It grows from inner surface to center in a gemstone. Usually geode found in Amethyst,White Chalcedony and Peridot stones.
Girdle Girdle is the widest part or outer edge of the gemstone and the dividing line between the crown and pavilion. The girdle can be rough (matt), faceted, polished or unpolished but a polished or faceted girdle doesn't improve a gemstone's grade. Most labs grade a girdle's thickness, not its appearance and the descriptions of girdle thickness range as follows: extremely thin; thin; medium; slightly thick; thick; extremely thick.
Girdling Girdling is the process of giving a circular shape to a gemstone. In this process, a gemstone is held in a lathe, or in a cutting machine, and cut or shaped by another diamond or tool, called a
Greasy (luster) One of the the technical terms used to refer to the luster of a gemstone. Jadeite is an example of a gem with a greasy luster.
Grading Report A grading report or certificate is a statement, issued by an independent Gemological Laboratory, that at the time of evaluation, the gemstone in question has been examined, measured, and scrutinized by experienced gemologist and graders, using various gemological instruments, and determined to contain the characteristics as stated in the Report or Certificate. The grading report should accurately describe the proportions, weight, color, clarity, symmetry, polish and possible fluorescence seen in the gemstone.
Habit It is the attributes of crystal's or aggregate's appearance.
Hue Refers to the position of a color on the color wheel, or the dominant wavelength of color attributed to a gemstone. There are six primary hues: violet, blue, green, yellow, orange, and red. In between these primary hues are secondary hues, such as blue-green. See also tone and saturation.
Hardness The hardness of a gemstone refers it's resistance to scratching on a smooth surface. Moh's scale of hardness, which scales from 1 (very soft) to 10 (very hard), is useful for comparing the relative hardness of different gem materials. Diamond is the hardest known substance on Earth and it is graded 10 on Mohs’ scale of hardness. Hardness is directional in most gemstones.
Heart Cut The Heart shaped gemstone is essentially a pear-shaped with a cleft at the top and which typically contains 59 facets. Due to the complexity of the shape, skilled cutting is necessary to maintain the gemstone’s brilliance. Generally people prefer a heart shape stone for sentimental purposes. This shape is mostly used in pendants, but also suitable for most jewelry items.
Hemimorphic It is in reference of a doubly terminated crystal which has two differently shaped ends.
Heat Treatment The application of high heat to a gemstone in order to improve its color and clarity or remove flaws.
Hexagon It is a term for polyhedron with six sides and a top and bottom base.
Hexagonal (crystal system) It is for any of the mineral that has four axes out of which three are equal in length and lie at an angle of 120° from each other. The fourth one may be long or short but at right angle toward the other corners.
High Polish It is a surface which has been polished to a mirror-like finish.
Hopper It is a form of crystal which exhibits an indenting, terraced, structure penetrating towards the center.
Idiochromatic Gems The colors in these idiochromatic gems come from elements that are an essential part of their chemical composition. These gems generally have only one color, or show a very narrow range of colors. Peridot is an idiochromatic gem, which is always green, due to one of its essential elements, iron.
IGI (International Gemological Institute) is an organization which offers a grading report for all gemstones. IGI has laboratories located throughout the world, including New York, Antwerp, Mumbai, Bangkok and Tokyo.
Igneous Rocks These are rocks that are formed from erupted volcanic lava or solidified magma
Inclusion An internal imperfection or characteristic which reduces the clarity or brilliance of a gemstone. Common gemstone inclusions are feathers, crystals, fractures, needles, graining, pinpoints and cavities.
Inlay This term refers to a decorative feature of an item of jewelry. An inlay is a piece of material (usually stone or glass) that is partially embedded in another material (usually metal) and these two materials make a level surface.
Intaglio Intaglio is a style of carving in which the design is carved into the surface of an engraved stone so that the rim shows the highest portion.
Internal Graining A gemstone which contains internal irregular crystal growth is known as internal graining. It may appear milky like faint lines or streaks.
Iridescent An iridescent material displays many lustrous, changing colors caused by the reflection of light due to inclusions in gemstones.
Iridescence A play of color effect caused by the interference of light on thin films within the gemstone.
Indicolite Blue tourmaline. From bright blue hues to bluish green colors, indicolite tourmaline is one of the rarer tourmaline colors.
Iolite It is a mineral which is used as a gemstone. It occurs in deep blue, purple, light blue-gray, and yellow-white.
Irradiation Exposing gemstones to radioactive rays from x-rays or other material to change or enhance the original color. Blue topaz is always irradiated, for example.
Jade Jade is a semiprecious stone, which is often used to describe jadeite and nephrite both as these two are similar in appearance and use. It is available in varieties of shades like green, light purple, yellow, pink, creamy white etc. Although this stone is found at many places but the best quality jade comes from Myanmar (formerly Burma). Jade is quite a hard stone with 6.5 to 7 on the Mohs scale and used in many jewelry items.
Karat Karat (as distinguished from Carat) is a measure of the purity of gold. Most gold jewelry is actually made from a gold alloy containing gold and another metal or metals. 18K gold, for example, is 75% pure gold.Karat is the American and Indonesian spelling of carat which is now only used for gold or gold alloys weight whereas English spelling carat is used in respect of weight of gemstones including diamonds. Karat is always based on pure 24 karat gold and if a jewelry item contains 18 karat gold that means it has eighteen parts pure gold and six parts other metal alloys.
Lab Created Refers to gemstones created in a laboratory rather than by nature. A lab created gemstone is typically the same material chemically as its natural counterpart, as in the case of corundum produced by flame fusion or quartz grown using the hydrothermal method.
Lapidary The science and art of cutting and polishing gems to their finished state.
Loupe It is a small magnifying lens which is used to observe certain aspects of gemstone. It commonly have a magnification level of 10x.
Loupe Clean A gemstone is said to be loupe clean when no inclusions or defects are visible when the gem is viewed with 10 times magnification. See also Eye Clean.
Luster The quality of reflected and refracted light from the surface of a gemstone or pearl. Luster is mainly dependent on stone's surface (polish) and the reflective index of the mineral. Luster can be described as: adamantine, pearly, greasy, metallic, silky, resinous, vitreous, earthy (also known as dull) and waxy.
Macrocrystalline It is a term for having large crystals which can be easily seen with a naked eye.
Matrix It is a material which has an embedded crystal inside or emerging from it.Matrix is a rock in which gemstones are found. It is also referred as the host rock or parent rock.
Matte It is a term which refers to a non-shiny, frosted surface.
Mafic It is a term used for describing the dark colored rocks or minerals which is composed of magnesium and iron.
Marquise The marquise shape is an elongated oval with points on both ends. Said to be named after the Marquise de Pompadour, the mistress of King Louis XV.The Marquise Cut is a traditional shape having elongated ends at both edges. The pointed ends make this shape the most fragile and the most expensive of brilliant style cuts. It has a total of 56 facets and construction of facet requires a lot of experience and delicacy of the sharp points demand utmost precaution. Now-a-days this shape is very popular for engagement rings.
Melee It is a term used generally to describe small, round faceted diamonds or the colored stones of approximately 0.18 carat or less.
Metamorphic Rock A metamorphic rock is a result of a transformation of a pre-existing rock. The original rock is subjected to very high heat and pressure, which cause obvious physical and/or chemical changes. Examples of these rock types include marble, slate, gneiss, schist.They can be formed by pressures deep inside the Earth, by tectonic processes such as continental collisions, or when they are heated up by an intrusion of hot molten rock called magma from the Earth's interior.
Metallic (Luster) One of the technical terms used to refer to the luster of a gemstone. A gemstone that is reflective like polished metal is said to have a metallic luster. Hematite is one of the rare examples.
The Mohs Hardness Scale A numerical scale ranging from 1 to 10 developed by Friedrich Mohs that assigns a rating to a gem according to its ability to resist scratching. The hardest is 10 (diamond) and the softest is 1 (talc).
Mohs Scale It is a loose scale of hardness devised by a German mineralogist, Friedrich Mohs in the 19th century. It is used for field collecting, which allows for identification of specimens. The comparative scale of hardness is as follows:
8) Topaz and Beryl
Mollusk It is a family of marine creatures having soft fleshy body surrounded by a calcareous shell. It includes the oyster and snail.
Mounting It is a trade term for particular portion of a piece of jewellery in which a gem or other object is set.
Multicolored It is term for exhibiting two or more of colors on a single specimen.
Nacre It is the secretion of iridescent substance by a mollusk during the formation of a pearl. It consists of layers of aragonite and calcite crystals.
Natural Gemstones These have been formed in natural environment with no interference by human. They form in a variety of ways in many different environments from many different chemical compounds. By the time they appear in our jewelry they've been cut or polished, but they've not been treated or altered in other ways.
Synthetic Moissanite A lab-created diamond simulant based on the structure of natural moissanite. On the Mohs scale of hardness, moissanite is 9.5. It has more brilliance, fire and luster than any hard jewel on earth, including diamond.
Oiling Oiling infuses colorless oils, resins or waxes into tiny surface-breaking fissures to hide them and give certain gemstones a cleaner appearance. This long-practiced clarity enhancement is used mainly for emerald and jade. The oils used are either natural or have a natural counterpart. If coloring agents are added to the oil, the stones are classified as dyed rather than oiled.
Onyx Onyx is a beautiful gemstone composed of chalcedony (a variety of quartz) and available in colors like black, white, black with white bands, red, brown etc. Onyx which is available in a red, brown or reddish brown color is known as Sardonyx. The bands that are found on this stone run parallel and are consistent. It is extremely similar to Agate, another variety of quartz. Agate bands are round or circular and are not consistent. Its hardness in between 6.5 to 7 on Mohs hardness scale and it is mainly found in Indonesia (Tulung Agung-Eastern Java),Madagascar, India, Brazil, United States, Pakistan and Sri Lanka.
Opaque A term used for gemstones that light cannot be seen passing through. Lapis lazuli and malachite examples of opaque gemstones.
Opal It is a non-crystalline, iridescent silica.Containing Hydrated Silica. It is the birthstone for the month of October.The name Opal is derived from three sources: Sanskrit ‘Upala’, Latin ‘Opalus’, and Greek ‘Opallios’. All three of these words mean the same thing – precious stone. Opal is made from sand and water. It has the same chemical formula as quartz with the addition of 3 to 10 % water content. This is a very popular gemstone, mainly due to its wonderful variety of rich and beautiful colors like black, white, gray, yellow, red, orange and colorless. High quality opals have an extraordinary feature of opalescence in which light reflects and bounces around the very small structures of the stone, giving it a wonderful aura and sometimes iridescence. The group of fine Opals include quite a number of wonderful gemstones which are differentiated on the basis of the variety, place of occurrence, and color of the main body, into Dark or Black Opal, White or Light Opal, Milk or Crystal Opal, Boulder Opal, Opal Matrix, Mexican and Fire Opal. Its hardness in between 5 to 6.5 on Mohs hardness scale and it is mainly found in Banten (Indonesia),Australia, Brazil, Mali, Japan, Russia, USA and Mexico. Australia is the major supplier of Fine Opals and almost 95 per cent of all Opals come from Australian mines.
Opalescence Opalescence is a kind of light play that happens with certain high quality stones. In these stones, light reflects and bounces around the stone structures which give them a wonderful aura and sometimes a milky blue form of iridescence.
Opaque Opaque refers to the transparency of a gemstone. Generally opaque stone does not transmit light as it is so thick with inclusions or flaws and due to that light is blocked from passing through the gemstone.
Optical Effects Some gemstones exhibit extraordinary optical effects known as phenomena. These rare and beautiful effects very often add value to gemstones. Some of these popular phenomena are Chatoyancy (cat's eye effect), Asterism (star effect), Color Change, Aventurescence and Iridescence.
Organic Gem Gemstones made by or derived from living organisms are known as organic gems. These include pearls from oysters, amber from tree resin etc.
Organic (gemstone) Most gemstones are minerals with a crystal structure but some gems, such as amber and pearl, are organic rather than mineral, being formed by plants and animals. See also Amorphous gemstones.
Padparadscha Derived from the Sinhalese term for "lotus flower," padparadscha refers to a lush pink and orange sapphire resembling the color of the lotus. Padparadscha is also sometimes used to refer to other types of gemstones, such as topaz and tourmaline, with this unique coloration.
PANCAWARNA is rock that has 5 colors ... The name is usually provided by the community Indonesia
Paraiba A rare copper-bearing tourmaline with an intense blue or blue-green color, first found in the state of Paraiba in Brazil in 1989. There have been recent finds in Nigeria and Mozambique of similar material, and the term "paraiba" is now used to refer to all examples of this copper-bearing tourmaline. See also Copper-bearing.
Pavilion The lower portion of a gemstone that begins just below the girdle.
Pear Cut Resembling a pear or teardrop, this fancy cut is rounded at one end and pointed at the other.
Peridot Peridot, a variety of mineral olivine, is a very old but still very popular gemstone. Peridot is formed deep within the earth under tremendous heat and pressure. The color of peridot is an integral part of its structure. Chemically peridot is an iron-magnesium-silicate and its intensity of the color depends upon the amount of iron contained by it. It is available in only one color shade with colors like yellow green, olive and brownish green. This gemstone is in fact identified by three names, Peridot, Chrysolith and Olivin. Its hardness in between 6.5 to 7 on Mohs hardness scale and it is mainly found in Australia, Mexico, Sri Lanka, South Africa, Tanzania, China, Burma, Arizona, USA, Pakistan and Afghanistan.
Phenomenal Gems Gems that display unusual optical properties such as color change, chatoyancy, asterism or iridescence.
Pigeon's Blood Refers to the most prized color of red in rubies. Pigeon's blood red is thought to be a pure red with a hint of blue. It is associated most with rubies from Burma, though any ruby could be this color.
Pleochroism The ability of certain gems to display two or more colors when viewed from different angles. This is a term also used for dichroism and trichroism.
Plotting Diagram It is a schematic diagram included on the EGL USA Diamond Certificate. It illustrates the facets, printed in black, of a diamond and the approximate location and type of internal and external characteristics, printed in red and green.
Point A gemstone unit of weight equal to 1/100 of a carat.
Portuguese Cut The Portuguese cut refers to a particular type of faceting where the gem is cut with three rows (simple cut = two rows) of rhomboidal and two rows of triangular facets above the girdle (crown) and four rows of rhomboidal and one row of triangular facets below the girdle (pavilion). The Portuguese cut thus has an extra row of facets on the crown, and this style enhances the brilliance of the gem. The Portuguese cut is one of the most popular fancy cuts in the market and you'll find many varieties of gems cut in this style.
Precious (gemstone) Traditionally, the four precious gemstones are diamond, ruby, sapphire and emerald. But other gems have also been labelled precious at times, including opal and amethyst. Today, the distinction between precious and semi-precious gems has been rejected by some gem trade associations. See also Semi-Precious gemstones.
Purity Purity is also known as clarity which describes the absence or presence of flaws inside or on the surface of a gemstone. For diamonds, purity is graded from F (flawless) to I3 (included 3) whereas for other colored gemstones, purity is classified into three ‘Types’. Type I colored stones include stones with very little or no inclusions, Type II colored stones include stones that often have a few inclusions whereas Type III colored stones include stones that usually always have inclusions.
Reflection The term reflection is used for important optical effect where light bounces or returns once it strikes the surface of a gemstone.
Refraction The term Refraction is also used for optical effect where light deviates or changes its direction once it enters in a gemstone.
Refractive Index (RI) When light meets the surface of a polished gemstone, some of the light is reflected, whereas most is absorbed. This entered light in the gem slows down and is bent from its original path due to the difference of density between air and gemstone. This process is known as refraction. This refraction varies from gem to gem depending on density and can be measured and used to help identify the gem type. This measurement is known as refractive index (RI).
Refractometer Refractometer is a device that is used to measure the refractive index of gemstones.
Rough The term rough is used for any uncut or unpolished gemstone.
Round Brilliant Cut The round brilliant cut is one of the most traditional and popular shapes. It has 58 facets which offer great brilliance and stability. These 58 facets include 1 table, 8 bezel facets, 8 star facets, 16 upper-girdle facets on the crown, 8 pavilion facets, 16 lower-girdle facets, and usually a culet on the pavilion, or at bottom. This cut is considered as ideal for a diamond because it maximizes a stone's sparkle.
Rough In gemology, this refers to the raw, natural state in which gems are found, before they are cut.
Ruby Ruby is the red variety of the mineral corundum and known for its magnificent color, excellent hardness and outstanding brilliance. Only red corundum is entitled to be called ruby, all other colors being classified as sapphires. This stone is available in colors like bright red, brownish-red, purplish-red, dark red and blood red. The name ‘Ruby’ comes from Latin ‘Rubens’ which means ‘Red’. In Sanskrit, the ruby is called ‘Ratnaraj’, meaning ‘the king of precious stones’. This gemstone has excellent luster, rarity and durability. Its hardness is 9 on Mohs hardness scale and it is mainly found in Burma, Thailand, Sri Lanka and Tanzania. Transparent rubies of large sizes are even rarer than diamonds.
Rubellite Used to refer to the red variety of tourmaline, including the color range from pink to red. More of a marketing than a gemological term; these days gemologists tend to use simply "red tourmaline."
Rutile Needle-like inclusions (or foreign matter) within stones. These can produce some gem phenomena such as asterism (star) or cat's eye (chatoyancy).
Saturation Saturation is one of three characteristics used to describe the appearance of color. Saturation (also known as intensity) refers to the brightness or vividness of a color. See also hue and tone.
Sapphire Sapphire is a variety of the mineral corundum and represents all the colors except red corundum, which is ruby. Its physical and chemical properties are virtually similar to properties of ruby. Blue is the main color of the sapphire whereas this gemstone is also found in colors like yellow, green, orange, pink, gray, colorless, black, brown, and purple. The word ‘Sapphire’ in its plain context refers only to blue sapphire, unless a prefix color is specified. Sapphire is one of the most desirable gems due to its color, hardness, durability, and luster. Its hardness is 9 on Mohs hardness scale and it is mainly found in Sri Lanka, Thailand, Burma, Australia, India, Brazil and Africa.
Sardonyx Onyx which is available in a red, brown or reddish brown color is known as sardonyx.
Saturation A color's position in a gemstone on a neutral to vivid scale.
Secondary Deposit Minerals and/or gemstones that have been separated from their original host rock, usually due to effects of weather, and deposited elsewhere. An alluvial deposit is an example of a secondary deposit.
Semi-Precious (gemstone) Traditionally, the four precious gemstones are diamond, ruby, sapphire and emerald. Semi-precious gemstones include everything else. But other gems have also been labelled precious at times, including opal, amethyst and pearl. Today, the distinction between precious and semi-precious gems has been rejected by some gem trade associations. See also Precious gemstones.
Semi-mount A style of jewelry setting that has the side stones already mounted, but which contains an empty set of prongs which are intended to mount a center stone as per the customer’s choice.
Shape A gemstone cut by shape describes the outline of the stone and pattern of the facet arrangement. Gems are available in various shapes like Modern Round Brilliant, Emerald, Princess, Heart, Oval, Pear etc. Round brilliant is the most popular shape for all jewelry items. All other non-round shapes are called fancy shapes.
Simulant,Simulated Stones Simulated stones can be anything that resembles a natural gemstone but does not have the same physical characteristics or chemical composition. These items are also known as imitation stones and usually much less expensive than the natural forms. Simulated stones are often made of glass or plastic and most can be detected easily by a jeweler.
Sheen This effect resembles luster, and is caused by light reflection from inclusions or texture inside the gem. Luster is light reflected from the surface of the gem and sheen is reflection from inside the gemstone.
Side Stone Side stones are set around or beside the center stone in a jewelry setting.
Single Cut Stones with seventeen facets or fewer.
Single Refraction Most gemstones are doubly refractive; they have two refractive indices. Only a few gemstones have a single refractive index, specifically diamond, spinel and garnet. See also Birefringence.
Solitaire A solitaire, often found in rings and pendants, is a single stone in a simple setting. Compare Center Stone and Side Stone.
Sparkle Sparkle is the combination of gemstone’s fire and brilliance.
Species The term used to designate a family of gemstones. For example, corundum is a species that contains the varieties sapphire and ruby. The quartz family contains amethyst, citrine, and chalcedony, to name a few.
Specific Gravity Specific gravity of a gem is an indication of its density. It is calculated by comparing the gemstone's weight with the weight of an equal volume of water. The greater the specific gravity of a gem, the heavier it will feel.
Step Cut A gem cut with rectangular facets along the perimeter.
Swiss Cut A gem cut consisting of thirty-three facets.
Synthetic (gemstone) A synthetic gemstone is man-made rather than mined from the earth. Natural gemstones that are treated by industry-accepted methods such as heat or irradiation are not classified as synthetic.
Symmetry Symmetry is an important aspect of the gemstone cutting process which refers to the balance of the outline shape and alignment of the facets. It is graded as Ideal, Excellent, Very Good, Good, Fair or Poor.
Table The flat top part of a gemstone. The table is the largest facet.
Tanzanite Tanzanite is a blue variety of the gemstone zoisite and named after the East African state of Tanzania, the only place in the world where it has been found. It is a trichroic gem which displays three layers of color. The colors dark blue, green-yellow and red-purple can be seen. Tanzanite is a beautiful gemstone, known for its brilliance but on the other hand it is a delicate gemstone which comes in between 6 to 7 on Mohs hardness scale.
Tone One of three characteristics used to describe the appearance of color. Tone refers to the lightness or value of the lightness in a particular stone. See also Saturation and Hue.
Topaz Topaz, a member of quartz family, is a beautiful gemstone that most commonly is found in yellow color. It is also available in various other colors like blue, brown, green, orange, pink, red, white, gold, colorless etc. The name topaz is derived from the Sanskrit word ‘Tapas’, meaning ‘Fire’. Topaz, with 8 on Mohs hardness scale, is considered tough and durable gemstone but still is not an invincible stone. It cracks and chips easily than many other gemstones. It is mainly found in Brazil, Sri Lanka, Burma, Nigeria, USA, Australia, Madagascar and Mexico.
Tourmaline Tourmalines are gemstones with deep brilliance and an incomparable variety of colors like black, red, pink, blue, green, grey and yellow. These Gemstones are mixed crystals of aluminium boron silicate with a complex and changing composition. The name tourmaline comes from the Singhalese words 'tura mali', means something like 'stone with mixed colors'. Tourmalines with different colors have different names. It comes in between 7 to 7.5 on Mohs hardness scale and it is mainly found in Brazil, Sri Lanka, South Africa, Nigeria, Zimbabwe, Kenya, Tanzania, Mozambique, Madagascar, Pakistan, Afghanistan and USA.
Translucent A quality of a gemstone transmitting light imperfectly so that one cannot see through the stone clearly. Star sapphire is an example of this quality.
Transparent There are several ways a light travels through a stone. In a transparent stone, the light travels through stone with virtually no distortion. Transparent stones are clear and easy to see through. See also Translucent and Opaque.
Transparency, also known technically as diaphaneity, is a function of the way light interacts with the surface of a substance. There are only three possible interactions. If the light enters and exits the surface of the substance in relatively undisturbed fashion, then the substance is referred to as transparent. If the light can enter and exit the surface of the substance, but in a disturbed and distorted fashion, then the substance is referred to as translucent. If the light can not even penetrate the surface of the substance, then the substance is referred to as opaque. Many substances that are transparent can easily contain flaws and distortions that will limit a light beam's travels through a
Treated stone A stone that has been heated, dyed, irradiated, or stained in order to improve the color or the clarity. Also pertains to gems that have their cracks or fractures concealed by filling the material.
Trichroism A property of a stone that will show three colors when the stone is viewed through a dichroscope.
Trichoric Trichoric refers to a gemstone that displays three different colors or shades when viewed from different angles or directions.
Trillion Cut A faceted cut in a triangular shape with 44 facets.
Vitreous A technical term referring to the luster of a gemstone. Gemstones with a vitreous or glassy luster are by far the most common in the gems world.