Metal Glossary

Precious Metal Guide – Metal Glossary

Knowledge of precious metals will bring you to further questions and make you inquisitive about the various terminologies associated with metals and its jewelry. To quench this thirst of knowing more, you can visit our Metal Glossary.

Term Description
Acid Etching This process involves engrossing the metal in an acid solution while protecting certain parts with a substance like wax or rosin, which is known as resist, in order to create a pattern on the metal’s surface.
Acid Test Acid test determines the purity of gold through the use of nitric acid and aqua regia.
Actual Gold Content Actual gold content describes the amount of gold that exists in a metal object after subtracting all the alloys.
Ag The chemical symbol for silver.
Alloy An alloy is a mixture of two or more metals usually mixed to enhance the strength and/or appearance of a particular metal. Copper, silver, nickel, zinc etc are frequently used as alloy metals and usually are mixed with all precious metals for some specific purpose.
Alpaca It is a mixture of alloys, which is a substitute of silver, consisting of 55% copper, 20% nickel, 20% zinc, and 5% tin.
Aluminum It is an inexpensive, lightweight and malleable silver-white ore with a bluish tinge. Aluminum is remarkably resisted to oxidation and used in many alloys.
Annealing It is a process of providing multi-phased heat and stress treatment that alters the microstructure of a metal adding strength, pliability and hardness.
Anodizing Anodizing is a process used to dye and/or modify the surface of a metal using electrolysis. The dye enters the pores in the etched oxide surface of the metal. Usually metals like aluminum, magnesium, titanium and tantalum are often anodized.
Assay An analysis of a metal to determine its purity by scraping a bit of metal from the metal piece.
Au The chemical symbol for gold. Au is derived from Latin word ‘aurum’ for gold.
Base Metal Base metal is a term used to refer any non-precious metal. Generally it is used as a base for gold-filled or gold plated coverings.
Blending Blending is a process of smoothing rough areas of a metal piece to provide same plane or roundness and/or same surface finish.
Bloomed Gold This term is used for gold jewelry that has been engrossed in an acid bath to give slightly matte texture.
Brass An alloy, made up of roughly half copper and half zinc, which has a nice yellow color.
Bronze Bronze is a very heavy and dense alloy consisting of 60% copper and 40% tin. It has a dull brown color and usually not preferred in jewelry due to its heaviness.
Brushed Finish A brushed finish, also known as matte finish, is a texture applied to metal surface, which gives a dull and non-reflective finish. In this finish, a firm wire brush is used to give scratches or tiny grooves on the surface of the metal piece.
Buffing Buffing is the process refers to the use of grease compound in combination with wheels to produce very smooth polished surface. It is the final step in professional finishing process.
Bullion Bullion is a precious metal usually gold in form of bars containing at least 99.5% purity.
Bullion coin Bullion coin is a precious metal in the form of coin which trades at a price close to spot. In other words, it has little or no numismatic value.
Burn Burn refers to changes in metallurgical properties and other physical characteristics such as discoloration of the metal piece due to excessive temperature during grinding.
Burnishing Burnishing is a finishing with shiny surface usually resulting from using a dull or loaded grinding wheel or coated abrasive.
Burr Burr refers to a sharp edge of metal which remains on the surface of metal after cutting and reforming.
Cameo Cameo is a style of carving in which the design pattern is left and the surrounding surface is cut away leaving the design in relief.
Carat The term Carat is used as a standard unit of measurement of the weight of most gemstones including diamond. One carat (ct.) equals 200 milligrams, or 0.2 grams (1/5 of a gram), or 1/142 of an ounce. It is different than the term Karat which refers to the fineness of pure gold and gold alloys.
Casting Casting is a widely used jewelry manufacturing process, in which a molten material such as metal, plastic or any other material is poured or forced into a hollow mold and allowed to solidify within the mold and then ejected or broken out to get a fabricated jewelry part.
Centrifugal Casting Centrifugal casting is the process of casting in which molds are attached to the outside edge of a hollow tube. Metal in liquid form is poured into the tube and it is spun at high-speed centrifugal force that pulls the molten metal into the molds.
Chasing A method of decorating or designing surface of the metal by etching or hammering using shaped punches and a chasing hammer.
Chrome Plating Chrome plating is a method of depositing a thin layer of chromium on other metal surface mainly for giving a bright and lustrous metallic surface, which is highly resistant to tarnish.
Chromium Chromium is a lustrous, hard brittle, steel-blue metallic element which is highly resistant to corrosion and tarnishing. It is generally used in the hardening of steel alloys and the production of stainless steels.
Cleaning Cleaning of metal casting refers to all activities that are performed to remove sand, scale and / or excess metal from the casting.
Coin Silver A mixture of 90% pure silver and 10% metal alloy is known as Coin Silver. A process of melting down coins done in the 19th century, and mostly discarded today.
Colored Gold Colored gold term is used gold when it is mixed or alloyed with other metals, such as silver, copper, zinc, nickel, platinum, palladium etc to create various color hues like white, pink/ rose, green and the seldom found blue, purple and black.
Comex Comex is one of the world’s major commodities futures exchanges where gold and silver are traded. It is a division of the New York Mercantile Exchange based at New York.
Conductivity Conductivity is the ability of a mineral to transmit heat, electricity or sound.
Coolant Coolant is a metalworking fluid used in grinding process to prevent a metal piece from burning as well as to lubricate for the process.
Copper Copper is a reddish-brown non-ferrous metal, which is usually considered as a base metal or alloyed with other precious metals. It is fairly soft metal with excellent conductivity of heat and electricity as well as it is very malleable and ductile. Other than jewelry, it is widely used for electrical wiring and water piping. The chemical symbol for copper is Cu.
Cu The chemical symbol for copper.
Deburring It is a method of removing burrs from the metal piece by using various hand and automated processes. Coated abrasives, non-woven products and stones are typically used for deburring.
Density The density of a substance depends on both its mass and its volume. For example, lead is denser than feathers, so 1 tonne of lead will have a lesser volume than 1 tonne of feathers.
Die An engraved metal object, usually of a hard metal such as steel, bronze or brass, used to strike or stamp the design on another metal object.
Die Struck Die struck is a process of reproducing an object by pressing or striking a piece of metal between a pair of dies. This pair consists male and female patterns to form highly detailed impressions on that metal piece.
Dwt Dwt is used as a symbol for ‘pennyweight’ that is 1/20th of a troy ounce or approx 1.555 grams.
Electroplated This term is generally used for jewelry items that have been coated with gold through the process of electroplating.
Electroplating Electroplating is the process where inexpensive metals are frequently electroplated or coated with a thin layer of more expensive metals like gold (gold plating), silver (silver plating), rhodium (rhodium plating), copper (electro coppering) etc. In this process, an electric current is flown to coat an electrically conductive metal object with a relatively thin layer of precious metal.
Enamel Enamel is a colored, opaque glassy material fused onto metal, pottery or glass to achieve a vitreous or glass-like, decorative surface.
Engraving Engraving is a method of surface decoration in which a design is etched or engraved with a sharp tool.
Etched It is very faintly carved decoration scratched onto the surface of a metal piece.
Findings Jewelry findings are basically components, materials and elements such as clasps, pins, hooks, tabs etc that can be used in making or assembling a piece of jewelry.
Fineness Fineness refers to the purity of a precious metal. The purity of a precious metal measured in 1,000 parts of an alloy. For example, a gold bar, containing 995 parts gold and 5 parts of another metal alloy, is considered with .995 fineness.
Finish The way the surface of a piece is cleaned or polished or textured. Finish refers quality of polish and symmetry on a gemstone as well as polish or texture applied to the metal on an item of jewelry. Common metal finishes include florentine, high polish and matte or brushed.
Florentine Finish A Florentine finish is a crosshatched decorative technique engraved into the surface of a precious metal. It is usually applied by a hand tool and consists a series of parallel lines engraved in two directions perpendicular to each other. This finish reduces the reflectivity of metal and the lines are often coarser and more deeply incised than the brushed or matte finish methods.
Foil Foil is a paper like thin sheet of metal which is used to place behind a gemstone to intensify its brilliance.
Foiling A method of coating or placing silver, gold, or colored foil behind a gem in a closed setting to enhance its appearance as light is reflected by this. This is often done with rhinestones.
Forging Heating a metal to a temperature where the metal becomes malleable (red hot) or deforming its shape by compression or exertion of force (by hammering or cold forging).
Gallery Gallery is metal strips used to make settings for gemstones or used as a decorative design element in a piece of jewelry.
Gilding A metal object usually decorated with a thin layer of gold, gold foil or gold leaf.
Gold Gold is an extraordinary and rare precious metal, with an unmatched combination of chemical and physical properties. Gold is the most non-reactive of all metals and it does not oxidize under ordinary conditions. No other metal is as malleable as gold. Pure gold is very soft and pliable, and alloys of different other metals are combined with pure gold to enhance its durability and strength, as well as creating a blush in the gold’s appearance with different color tones. 24 karat is 100 % pure gold, and it is more expensive and less durable than gold that is alloyed with other metals.
Gold – 10 Karat (White Tone) Gold which combines 10 parts of pure gold and 14 parts of other metal alloys and appears in white tone.  Normally white gold is created by combining pure gold with a copper, zinc and nickel (or palladium) alloy.
Gold – 10 Karat (Yellow Tone) Gold which combines 10 parts of pure gold and 14 parts of other metal alloys and appears in natural yellow tone. By combining with copper and silver, yellow gold retains a rich yellow color while increasing its strength.
Gold – 14 Karat (White Tone) Gold which combines 14 parts of pure gold and 10 parts of other metal alloys and appears in white tone.  As mentioned above, normally white gold is created by combining pure gold with a copper, zinc and nickel (or palladium) alloy.
Gold – 14 Karat (Yellow Tone) Gold which combines 14 parts of pure gold and 10 parts of other metal alloys and appears in natural yellow tone. As mentioned above, by combining with copper and silver, yellow gold retains a rich yellow color while increasing its strength.
Gold – 18 Karat (White Tone) Gold which combines 18 parts of pure gold and only 6 parts of other metal alloys and appears in white tone.  As mentioned above, normally white gold is created by combining pure gold with a copper, zinc and nickel (or palladium) alloy.
Gold – 18 Karat (Yellow Tone) Gold which combines 18 parts of pure gold and only 6 parts of other metal alloys and appears in natural yellow tone. As mentioned above, by combining with copper and silver, yellow gold retains a rich yellow color while increasing its strength.
Gold Eagles It is referred as modern gold bullion coin. American gold eagle contains 91.7% pure gold (22 karat) and for the remaining part silver and copper as alloy.
Gold Filled Gold filled refers to a layer of at least 10-karat gold that has been permanently bonded by heat and pressure to the surface of the base metal, then rolled or drawn to a prescribed thickness. The karat gold must be at least 1/20 of the total weight. It is also known as gold overlay.
Gold Flashed A gold coating in which thickness of layer is less than seven millionths of an inch. It is sometimes also called gold washed.
Gold Plated Gold Plated refers to a thin layer of plating of 10-karat gold or better which has been bonded to a base metal. The karat gold content may be less than 1/20, but it must be properly identified by weight in terms of total metal content.
Gold Standard A monetary system in which currency can be redeemed or converted for a fixed amount of gold. The government or bank must have enough gold in reserve to redeem all its circulating currency.
Gold Tone In its pure form, gold has a metallic luster with deep yellow in color, but when it is mixed or alloyed with other metals, such as silver, copper, zinc, nickel, platinum, palladium, etc. then it creates various color tones like white, pink/ rose, green and the seldom found blue, purple and black. It is sometimes called gold color.
Golden finish Jewelry that does not contain actual gold but finished in such a manner that it has the look of gold jewelry item.
Goldsmith A person, who is an expert for working with precious metal to create jewelry.
Grain It is an earliest known weight unit for gold. One troy ounce contains 480 grains.
Gram Gram is the basic unit of weight of the metric system and generally used to express the weight of jewelry items. One troy ounce contains 31.1035 grams.
Green Gold Pure gold is mixed with silver, copper and zinc to get green gold. Although this color is not very popular but still it gives wearer an opportunity to look different.
Grinding Grinding is used to remove material from a work piece through machines and by using abrasive minerals.
Hallmark A hallmark is an official mark (or a series of marks) stamped onto a precious metal that indicates the fineness of the metal and the manufacturer’s mark. As well as sometimes hallmarks indicate the country and year of manufacturing. Although marks are not officially required in USA but usually they are carried by custom and practice.
Hammered Finish A hammered finish is a texture applied to the surface of a metal piece with a hammer to give it a dimpled look. A hammered texture gives impression of a series of small depressions in the metal. This finish is varied from light to deep hammering texture and usually increases the size of the metal piece.
Hand Made Hand made jewelry is created completely by hand and only some hand tools are used for this.
High Polish Finish High polish finish is a super shiny and smooth polish applied to a metal surface that gives a highly reflective and mirror-like finish.
Ingot An ingot is a metal cast into the shape of a bar or block.
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.
Iridium Iridium is a metal of the platinum family which often alloyed with platinum to improve workability. Jewelry pieces marked ‘80% Plat. 20% Irid’ would indicate that the alloy is containing 80 % platinum and 20% iridium.
Iron Iron is a very common metallic element and mainly used to make steel. It usually appears dark brown in impure form whereas silvery-white in pure form. Pure iron is quite soft and it is oxidized (rusted) easily by moisture. The chemical symbol for iron is Fe.
Karat, Karat Weight Karat is the American 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 diamonds or other gemstones. 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. Karat is also used in its abbreviated ‘kt’ form.
Lead Lead is a dense, soft metal with a dull blue-grey appearance. It has a low melting point and due to this it is generally used in soldering. The chemical symbol for lead is Pb.
Lost Wax Casting This is one of the most commonly used casting techniques. Under this casting method, an object is made of wax and coated in clay. When the clay is fired, the wax melts and is drained away or evaporates leaving an exact impression of the object in the hardened clay, which is then filled with molten metal.
Luster The quality of reflected and refracted light from the surface of a gemstone or metal. Luster is mainly dependent on surface (polish) and the reflective index of the mineral or metal. Luster can be described as: adamantine, pearly, greasy, metallic, silky, resinous, vitreous, earthy (also known as dull) and waxy.
Malleability Malleability is the physical property of metal that allows it to be hammered, rolled, compressed and stretched. Gold is the most malleable of all metals.
Matte Finish A matte finish, also known as a brushed finish, is a texture applied to metal surface, which gives a dull and non-reflective finish. Matte finish is achieved either by a chemical process or by using an abrasive material to scratch the top layers of the piece.
Metal Metal is a solid mineral element that usually has a shiny surface and generally a good conductor of heat and electricity, and can be melted or fused, hammered into thin sheets, or drawn into wires. Common metals include bronze, copper and iron whereas gold, platinum and silver are considered as precious metals and used for making jewelry.
Metal Etching A technique of creating a design on metal using acid. Some parts of the metal are covered and protected from the action of the acid, while the remaining exposed parts are eaten away by the acid to form a design.
Metal Type The type of metal that is used to create jewelry.
Milgrain It is a decorative technique in which a beaded design is impressed into the metal by using a special engraver’s tool.
Mirror Finish A highly reflective and mirror like finished surface with no visible abrasion pattern.
Mold Mold is the hollow form into which molten metal is poured to solidify and then ejected or broken out to get a fabricated jewelry part. It is made from a refractory material either for temporary use or for permanent use.
Nickel A multipurpose hard, bright, silver-white metallic element of the iron group that is malleable, ductile and resistant to corrosion. It is most commonly used in alloys and plating.
Nonmetallic An object or material which is not composed of metal.
Non-precious Metal Non-precious metal is any metal that is not considered to be a precious metal.
NYMEX NYMEX is New York Mercantile Exchange which is a future exchange where platinum and palladium are traded.
Ore An ore is a group of rocks containing valuable minerals that can be extracted.
Ounce A unit of weight. For precious metals, an ounce means a troy ounce which is equal to 31.1035 grams.
Overlay  Overlay is a type of jewelry decorative technique that involves two flat metal pieces. The top piece is highly polished whereas the bottom layer is darkened with oxidation to provide good contrast when the two pieces are soldered together.
Oxidation Oxidation is a chemical process in which a metal is blackened as a reaction to oxygen.
Palladium Palladium is a member of the Platinum group metal and it is lighter and less expensive than platinum. Palladium is usually mixed with yellow gold to create white gold.
Patina The change in an object’s surface resulting from natural ageing due to oxidation and wear.
Pennyweight Pennyweight, usually shortened by dwt, is an American unit of weight for gold. One pennyweight equals 24 grains or 1/20 of a troy ounce. Also a pennyweight is equal to 1.5552 grams.
Periodic Table It is a tabular method to classify, systematize and compare all the 116 (94 natural, 22 synthetic) basic chemical elements.
Pink Gold Pink gold, also known as rose gold, is alloyed with copper, and at times possibly even with silver. The proportions are about three parts of 24-karat gold to one part of copper.
Plating Plating is the technique to cover or coat a thin layer of a metal to another metal surface mainly for the decorative purposes.
Platinum Platinum, an extremely rare and expensive metal, is a silvery gray precious metal often used for setting or mounting high quality diamonds and gemstones. Platinum is a strong, durable and dense metal which is valued for its white color and purity
Plumb Gold It is a term used to describe gold jewelry that contains the precise amount of gold in the alloy that the karat mark indicates. A jewelry piece with 18kt plumb gold means that the gold will be at a minimum 18 parts gold mixed with 6 parts alloys.
Polish In terms of metal, polish is considered as smoothness of the surface of a metal object in which optical reflection is maximized.
Polishing Metal polishing is the process of rubbing a metal piece to make it smooth and shiny as well as reduce the appearance of flaws.
Porosity Porosity refers to the areas of the mold that absorbed some of the casting material and leaves the cast object with a rough, granular surface.
Pot Metal Pot metal, also known as white metal, is a mixture of alloys which does not contain any precious metal.
Precious Metal A precious metal is a metal with rare metallic chemical element. Gold, platinum and silver are widely traded and considered as precious metals due to their rarity, beauty and physical properties. Precious metals are less reactive than most elements, have high luster, and have higher melting points than other metals.
Relief Relief is a kind of decoration that projects from the surface, like a cameo.
Repousse A method of decorating a metal surface by pressing or hammering a design from the inside or backside and then polishing it up in front with a chasing hammer, producing a three-dimensional base-relief surface.
Reticulation It is a process of giving the metal surface a rough or wrinkled texture.
Rhodium Rhodium is a noble metal, from the platinum family, with a whitish gray appearance. Rhodium, in raw natural state, comes in liquid state and in jewelry industry, it is very popular plating metal which gives very smooth, shiny and expensive look, just like platinum, to a metal piece.
Rhodium Plating In this process, rhodium is applied through the electroplating process to base metals like gold, sterling silver or some other metal alloy. This rhodium plating gives silver tone finish, which is darker than a silver plated finish and darkens with time rather than tarnishing like silver plate. Rhodium plating is virtually identical to Platinum but on a fraction of the cost and often it is used on fashion rings and brooches.
Rolled Gold Rolled gold is a very thin layer of gold that is applied to a lesser or base metal usually brass. Rolled gold metal pieces are marked rolled gold plate or R.G.P. or RGP.
Rose Finish A type of finished jewelry that resembles to rose gold jewelry but actually does not contain any gold content.
Sand Casting Sand casting is the oldest and most popular casting technique. Under this technique, natural sand (lake sand) or green sand (mixture of sand, clay and some water) is packed onto wood or metal pattern halves, removed from the pattern, and metal is poured into resultant cavities. And finally, mold is broken to remove casting. This technique requires a lead-time of days to obtain castings.
Sand Blasting Sand blasting refers to the process of cleaning, smoothing or etching a hard surface by forcing very fine bits of solid material across that surface at high speeds.
Satin Finish Satin finish is a texture of a metal surface that is in between matte finish and a brilliant one. In this finish, a series of tiny parallel lines are scratched onto a metal surface with a wire brush or polishing tool to produce texture. This finish gives impression of a soft, pearl-like luster instead of a bright polish.
Scoring A technique of using a tool to engrave a groove or furrow into the flat surface of the metal.
Silver Silver has been known and used for thousands of years and it is considered as one of the three precious metals along with gold and platinum. Pure silver is very soft metal with its lustrous white color. Silver is used as jewelry metal well before the development of white gold alloys, and before platinum could be isolated. It is normally stable in pure air and water but tarnishes when exposed to ozone, hydrogen sulfide or sulfur. The chemical symbol for silver is Ag.
Silver – Coin A mixture of 90% pure silver and 10% metal alloy is known as Coin Silver.
Silver – Fine It is the purest form of silver with 99.9% purity. In this form, silver is too soft to be used for jewelry.
Silver – Mexican Silver from south of the border is known as Mexican silver, which consists anywhere from 90% to 99% pure silver.
Silver – Sterling A mixture of 92.5% of pure silver and 7.5% of copper is known as Sterling Silver. Pure silver is alloyed with copper to give strength and durability. It is one of the most familiar and used forms of silver alloys.
Silver Eagles It is referred as modern silver bullion coin.
Silver Finish Jewelry or any other item that does not contain actual silver but finished in such a manner that it has the look of silver jewelry item.
Silver Plating Silver plating is a method of depositing a silver layer on other metal surface mainly for decorative purposes on household and jewelry items.
Soldering Soldering is a technique, used by jewelers, in making and repairing jewelry. By using this technique, two or more metal pieces are joined by applying a molten metal or metal alloy that has a lower melting point than the two metals being joined. This molten metal forms a bond when cooled and solidified. Soldering is also used in adding findings or links in a metal piece.
Solid Gold As per the rules of the Federal Trade Commission, the term ‘solid gold’ can be used for items which are not hollow and contain at least 10 karat or finer gold.
Stainless steel An extremely durable metal alloy of steel and chromium that can be polished to resemble a precious metal and is almost unaffected to rust, discoloration and corrosion.
Stamping Stamping is the process of cutting or embossing a mark on metal sheet with a punch or a die.
Swage Swage is a technique which uses a tool or hammer to bend or shape a metal available in solid state.
Tarnish A dull metal finish or luster due to its exposure to air or dirt that discolors the surface of metal as well as due to reaction between metals and other chemicals which discolors the surface, particularly silver which reacts with sulfur. Tarnish is a form of corrosion.
Tin A silvery metallic element with a low melting point and resistant to corrosion, which is often used as soldering material and alloy for other precious metals. The chemical symbol for tin is Sn.
Titanium Titanium is an ultra-light but very strong and hypoallergenic metal comes in silvery color. In jewelry industry, it is generally used for wedding bands and watches.
Tola Tola is a unit of weight mainly used in India which is equal to 180 grains or 0.375 troy ounce or 11.7 grams. Usually gold bars are measured in tolas and the most popular of which is the 10-tola cast bar (3.75 troy oz).
Troy ounce It is a unit for measuring the weight of precious metal. One troy ounce equals 31.1035 grams or 480 grains (20 pennyweights (dwt) each of 24 grains)or 1.09711 avoirdupois ounces.
Tungsten In jewelry industry, Tungsten is a fairly new metal which often used for wedding bands. It is four times harder than titanium and resistant to corrosion.
Two-Tone A piece of jewelry that either uses both white and yellow metals or uses two different tones of same metal.
Vacuum Coating A coating process in which an extremely thin metallic coating is applied generally on very inexpensive metals, by volatilization within a vacuum.
Vermeil Vermeil refers to gold plating, with at least 10-karat gold, onto the surface of sterling silver. The finishing looks are very similar to pure gold jewelry and very hard to differentiate.
White Metal White metal, also known as pot metal, is a mixture of alloys which do not
contain any precious metal.
Yellow Gold Yellow gold is the most frequently seen and a timeless color. It is usually alloyed with silver and copper. Depending on the karat gold (14K, 18K or 22K), the color of yellow gold may vary from a softer shimmering yellow to a bright rich yellow. This is due to the varying alloy combinations. The color contrast of yellow gold is most suitable to diamonds and other delicately colored gemstones, as they can appear brilliant and vivid.
Zinc Zinc is a lustrous bluish-white metal from the magnesium-cadmium group and generally alloyed with other precious metals. This metal is also used for coating iron and steel to protect against rust. The chemical symbol for zinc is Zn.
Zn The chemical symbol for zinc.