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Inland Lapidary - Lapidary terms
Category: General technical and industrial > Gems and Jewels
Date & country: 24/10/2013, US
Words: 404


a jour
An open setting that leaves the pavilion facets of a cut gemstone open to the light

abrasive
Hard, tough material used to smooth out rough surfaces; a common abrasive is sandpaper.

accessory mineral
Mineral that occurs with other minerals.

aigrette
Refers to the tufted crest, or head-plumes of the egret, used for adorning a woman's head-dress and to an ornament, such as a spray of gems, resembling a tuft of plumes. Often worn in the hair or on a cap.

alloy
A metal that is manufactured by combining two or more molten metals. An alloy is always harder than its component metals. Common alloys used in jewelry are: gold under 24 Kt (mixed with silver, copper, and/or other metals), sterling silver (92.5% silver, 7.5% copper), brass (roughly half copper, half zinc), bronze (at least 60% copper with tin and perhaps other metals), and pewter (tin, lead, antimony, and a bit of silver or copper).

alpaca / alpacca
An alloy consisting of mostly copper (roughly 60 percent), and approximately 20 percent nickel, about 20 percent zinc, and about 5 percent tin. This metal is a a silver substitute.

amalgam
Any alloy of mercury and another metal. Some amalgams occur naturally. Note: There is a mineral known as Amalgam, and, although it is an amalgam, should not be confused with the term amalgam.

amber
The fossilized resin of prehistoric pine trees which ranges in color from golden to orange-red

amorphous
Without a crystalline shape. An amorphous gem, like amber, or ivory, does not have a regular internal structure, like those gems that fall within the seven crystal systems.

anisotropic
Lacking consistent hardness on all surfaces. For example, the hardness of Kyanite on the Mohs scale is between 6 and 7 lengthwise, and between 4 and 4

ankle bracelet, ankle chain, anklet
An ornament worn around the ankle.

anneal
The process of heating metal for a period of time to release the molecular changes created when it has been hardened either through work hardening or heat hardening. In jewelry making the heating is usually until the metal is red hot.

antique cushion cut
A gem shape similar to an octagon, but with all curved sides around the girdle.

appraisal
An individual's opinion as to the value of an item. This value can established for market value, replacement value, or insurance purposes. Usually each successive value class is somewhat higher than the previous listed category value.

arabesque
A form of decoration characterized by flowing lines, scrollwork, leaves, branches, floral forms, symmetrical in form.

arborescent
Synonym to dendritic: Aggregate composed of skeletal or tree-like formations. May be a single entity, or a formation that forms from mineral-rich solutions that deposit the mineral in rock and form a tree or plant structure embedded in rock. There sometimes is a distinction noted between the two aggregates; in some guides the former aggregate (single entity) is known as skeletal, and the latter as dendritic (embedded in rock). Other guides, such as this one, don't distinguish the two, and term them both as dendritic.

arcade setting
Also called coronet or ch

argos gold
Term used for any inferior quality jewelry. It is not necessarily bought from the United Kingdom retailer Argos, but view as low cost and flashy.

arm ring
A band of usually precious metal worn as an ornament around the biceps of the upper arm. Also called armlet or an armband.

art deco
A style popular from the mid-1920's until the 1930's. This style originated in Paris, France. Pieces are characterized by geometric lines and angles, with very few curves. This art movement eventually became bolder and evolved into Art Moderne.

art nouveau
A style popular from roughly 1895 until World War I. Pieces are characterized by curves and naturalistic designs, especially depicting long-haired, sensual women. Louis Comfort Tiffany made archetypal Art Nouveau pieces.

arts and crafts
An artistic movement that produced hand-crafted pieces toward the end of the 1800's. Pieces purposely look hand-made, incorporating hammer marks and simple cabochon settings. The Arts and Crafts movement also revived the art of enamel.

assay
The process that determines the proportions of precious metal contained in a piece of gold or silver. Meat used in jewelry making may display an assay hallmark identifying assayer.

asymmetrical
Not containing perfect symmetry.

auriferous
Containing gold.

axis
Imaginary line drawn through the center of an object, either horizontally or vertically. In the case of minerals, it is used to determine if and how mineral has symmetry. The horizontal axis is known as the x axis, the vertical axis as the y axis. Axis lines are usually drawn as dotted lines. Plural is axes.

axis of symmetry
An imaginary line drawn through the center of a crystal that replicates the exact shape if the crystal is turned to 360

bail
The portion of a pendent through which the chain or necklace passes.

bakelite
The trade name for the first synthesized plastic invented by Dr. Leo Backeland. It was the first plastic made from synthetic components (phenol and formaldehyde, generally with a wood flour filler) and was used in diverse products such as kitchenware, pipe stems, toys, and jewelry.

band
A ring that is made from a thin, flat, ribbon-like strip of material, usually metal. The band can be unadorned or decorated.

bangle
A bracelet variety designed to slip over the hand which moves around freely on the wrist. Often, several are worn at once so that they make noise when they bang together.

bar and ring clasp
Also called a toggle clasp is a jewelry fastener in which a bar can be inserted into a ring to fasten a piece of jewelry. It is used to attach the two ends of a necklace or bracelet.

barraco / baroque
Ancient Portuguese noun for a pearl that is an unpredictable or elaborate shape. Freshwater pearls are most commonly baroque but there are artificial versions. The term evolved into Baroque meaning elaborate and with may details.

barrel clasp
A jewelry fastener that resembles a barrel. The two pieces of this clasp screw together. It is used to attach two other rings or links of a necklace or bracelet.

basal
Having to do with the base.

basse-taille
French for

baton
A baton is a stone that is cut in a long, thin rectangular shape. A baton is larger than a baguette.

bell cap
A jewelry finding that is used to convert a hole-less bead or stone with into a pendant. A bell cap is glued onto the bead or stone and had a loop for attaching to the piece of jewelry.

bezel
1. The part of a cut stone that protrudes above the edge of a setting. The bezel is also known as the crown.

bib necklace
Also known as a collarette, is a short necklace with flowing ornaments in the front.

birefringence
Another name for double refraction where the light entering the stone is split into two light rays, and the rays travel in different paths.

birthstone
Gems assigned to different birth months, originally based on astrology. Many different lists exist today. You can view several at birthstones

bolt ring
A circular catch used for the fastening of necklaces or bracelet chains. It is a hollow or partly hollow connecting ring drawn back on a spring.

bort
Term for industrial grade diamonds.

boule
Synthetic gems created from molten liquids placed in tear shaped molds to crystallize, leaving them with a tear-like form. Mostly applied to synthetic Rubies and Sapphires.

bracelet
Any article of jewelry worn around the wrist.

brass
Man-made alloy of (at least 50%) copper and zinc. Originally any alloy of copper was known as brass and early brass was commonly an alloy of copper and tin. See also bronze. This alloy naturally oxidizes green.

brazilian chain
Also called a snake chain, it is a metal chain made up of a series of small, linked cups.

brilliant
1. Referring to cut: A type of cut used for certain gemstones, frequently diamonds. It has 56 facets, 32 facets are above the girdle, 24 are below and is also called a full or modern cut.

briolette
A teardrop shaped stone faceted with triangular or rectangular facets. May also be called a

brooch
A decorative jewelry item designed to be attached to garments. It is usually made of metal like silver, gold, bronze or some other material. They are often decorated with enamel or gemstones. They may be solely for ornament or serve a practical function like a fastener for a garment.

buff top cabochon
A cabochon where the pavilion is faceted and the top remains a smooth dome. (see cabochon below)

bulla
An ancient Roman pendant that consists of a rounded container holding an amulet (good luck charm) worn on a strap around the neck. ^top

cabochon
A gem or stone that has been cut into a shape with a flat bottom and has a highly polished, rounded , smooth dome top. (See our How To Cab online guide)

calibre-cut
Small stones usually cut in rectangular shapes and faceted in a step cut to fit exactly into a setting or against another stone.

calipers
Any of various measuring instruments having two usually adjustable arms, legs, or jaws used especially for fine measuring diameter or thickness.

cameo
Gem with a design or figure carved out of the stone, and raised above the background layer

carat
Weight measurement used in reference to gemstones in regard to their evaluation. A carat is .2 grams (or 200 milligrams), and this weight is used worldwide, even in the U.S. where the metric system isn't used. A point is the weight used only in reference to very small, precious gemstones, and represents 1/100th of a carat. The abbreviation for carat is Ct. and for point is Pt. The term carat in regard to gemstones should not be confused with the term carat in regard to gold. By gold, it refers to the content of gold a gold ornament contains. Because of the confusion, the term carat in regard to gold has been changed to karat.

carving
carving Ornamental figure, such as a stone lion, carved out of a rock or mineral. A piece of stone formed this way is described as carved.

casting
Filling a mold with molten metal to produce a form. Some metals can be poured into a mold, while others need to be forced into it through various methods such as spin casting, vacuum casting, or steam casting.

channel setting
A style of setting used for faceted stones in which channels are created in parallel strips, where the girdles of stones will fit. Creates a clean line of stones.

chasing
Technique of working a design into a metal from the front using a hammer and/or punches.

chatelaine
A girdle or belt from which various implements are suspended.

chatoyancy
Phenomenon of certain cat's eye minerals which causes it to exhibit a concentrated narrow band of reflected light across the center of the mineral. Chatoyancy is usually only seen on polished cabochons. Chatoyant is the ability to exhibit chatoyancy.

choker
A a tight-fitting necklace, worn high on the neck. It can consist of one or more bands circling the neck.

clarity
Term used in grading colored gems or diamonds to describe the level of internal inclusions, fractures or stress marks inside of the stone. Colored stone are assess with the naked eye, diamonds are graded under 10 power magnification.

claw
A metal prong that holds a stone securely in a setting.

claw setting
Setting in which a series of metal prongs, claws, holds a stone securely in a setting by gripping the the stone just above the girdle. There is no metal directly under the stone making it an open setting letting light in under the stone. Usually used for transparent, faceted stones. The modern-day claw setting became popular in the 1800's.

cleavage
The property some minerals have of tending to split along clean planes in one or more directions. Not all minerals posses cleavage and many can be cleaved in several different directions. Cleavage is related to the minerals crystalline structure. (see mineral properties)

cleavage angle
The angle, or side, that exhibits or has exhibited cleavage.

collet
Round band or flange of metal encircling a gemstone to hold it in place.

critical angle
The minimum angle at which a stone's pavilion facets can be cut to allow the light entering a gem to be reflected back out of the stone's crown, making the gem brilliant, instead of windowed. The proper critical angle varies, depending on a gem's refractive index.

cross facet
Small triangular facets above and below the girdle of a brilliant cut stone.

crown
The upper portion of a faceted stone from the girdle up to the top of the stone.

crystal
A mineral in which the systematic internal arrangement of atoms is outwardly reflected as a latticework of repeated three-dimensional units that form a geometric solid with a surface consisting of symmetrical planes. (see mineral properties)

crystalline
1) Having a crystal structure.

ct.
Abbreviation for carat

cut
1. n A description of the type of facet. Used to describe the quality of faceting evenness, diameter to depth proportions, and diameter to table proportions of a polished gem.

cymophone effect
Phenomenon seen on a few polished gems that cause it to exhibit a floating light reflection that moves as the gem is rotated. ^top

damascening
The inlaying of a soft metal like silver or copper into a hard metal like steel. The name comes from the city of Damascus, where this process was first used.

dead soft
Refers to very soft-tempered metal. For example, copper electrical wire is dead soft.

demi-parure
A matching set of jewelry, usually containing a necklace, earrings, and a pin.

dentelle
Rhinestones cut with 32 or 64 facets.

diadem
A semi circular band worn around the head (tiara). It is usually jeweled and three dimensional.

diamont
Another word for rhinestone.

dichroic / dichroism
The property of having more than one color, especially when viewed from different angles. Many minerals are naturally dichroic. This effect can be artificially caused by a thin layer of a metallic oxides that is deposited on the surface of a material. Dichroic coated glass transmits some wavelengths of light and reflecting others, giving it an opal-like appearance.

die stamping
A process in which sheet metal is cut and shaped between two dies, forming a pattern in relief. Two steel dies are used, the male die has the design in cameo (protruding); the female die has the design hollowed out. The male die is put on top of the metal, the female die is put on the underside of the metal. The press is forcefully brought down onto the dies and metal, forcing the metal into the shape of the mold.

diffraction
The bending of light when it enters from one medium into another. For example, light bends as it travels from air into another substance, such as water. Diffraction also occurs when light enters from the air into a mineral, and the amount of diffraction varies among minerals.

diffusion treated
Refers to process where stones are color-enhanced . This process only colors the outer surface of the stone, so chipping or re-polishing will result in a loss of color. Diffusion-treated stones are already-cut stones that are heated in the presence of other compounds (like iron oxide, chromium oxide, titanium dioxide, etc.) that will infuse the extreme outer surface stone with color. Under a microscope, you you can see the loss of color within each tiny scratch. Diffusion treatment can also change the stone's refractive index. Also, if the stone is faceted, the color will appear stronger where the facets meet.

divitrification
Changing over from a natural glass to a mineral with a crystalline structure. To devitrify is the process of a natural glass to lose its glassy nature and crystallize.

dop stick
A small stick or dowel on which stones are mounted temporarily so they can be secured for cutting. Sometimes just called a dop.

dopping wax
A hard wax used to attach the dop stick to the stone to be cut.

double refractive
The ability of some gems to split a ray of light into two separate rays, each traveling at a different velocity. This effect caused the pavilion faceting to appear doubled when the stones is viewed through the table.

doublet
A gem made from two layers in order to save expenses; the lower part of the composite stone is glass or a non-precious stone, the top is the more valuable stone. One common doublet contains a layer of real garnet and a layer of glass.

drop cut
A pear-shaped cut gemstone with triangular facets on top. Also called briolette, is a common form for a pendant.

druze
A layer of crystals that form within a mineral crust, like the inner cavity of a geode.

ductile
Substances easily pulled or stretched into a thin wire. Gold is the most ductile metal. ^top

EGL
Acronym for European Gemological Laboratory

electroplating
A method (also called Galvanotechnics after its inventor, Luigi Galvani) in which an electric current deposits a layer of metal on an object. For example gold electroplated over a less expensive base metal. The thickness of the metal coat varies. Electro-gilded coating is the thinnest (less than 0.000007 inches thick); gold-cased metals have a coating thicker that 0.000007 inches.

electrum
An amber-colored alloy of gold and silver that was used in ancient times. Electrum is also an alloy used in medieval times consisting of copper (50%), nickel (30%) and zinc (20%).