Abalone
A mollusc whose shell is iridescent on the inside. Abalone is a source of mother of pearl which is used in jewellery making. Also known for its delicious edible flesh.
Akoya pearls
One of the most familiar types of cultured pearls, grown in pearl oysters off the coast of Japan. They are known for their orient and warm colour and rarely grow to more than 9mm in size. Read more.
Alexandrite
A mineral (a type of chrysoberyl) that appears in different colours depending on whether it is viewed in natural or artificial light. It appears to be red when seen in candle light and blue to green when seen in fluorescent light. Alexandrite was discovered on the birthday of the Russian Czar Alexander II and was named in his honour. It is mined in Russia, Brazil, Myanmar, Sri Lanka, and Zimbabwe. Read more.
Alloy
A combination of two or more metals. Common alloys used in jewellery include gold with less than 24 carat (mixed with silver, copper, and/or other metals), sterling silver (92.5% silver, 7.5% copper), brass (roughly half copper and half zinc), bronze (at least 60% copper with tin and possibly other metals), and pewter (tin, lead, antimony, and a little silver or copper).
Amber
A translucent fossilised resin (from conifers) that comes in a range of colours including, yellows, reds, whites, blacks and blues. When rubbed, amber produces static electricity. The best quality amber is clear. Read more.
Amethyst
A relatively common form of mineral quartz. It is usually purple but can vary in colour from pale lavender to a deep, reddish purple. Deeper-coloured amethysts are more highly valued but synthetic ones are hard to differentiate from the real stone. Read more.
Amplitude
Maximum angle by which a balance in a watch swings from its position of rest.
Aquamarine
A transparent light blue or sea-green stone. Today, blue aquamarines are more highly valued, but this was not always the case. Large aquamarines are relatively common and the best ones come from Brazil. Read more.
Azurite
A mineral that is normally opaque and azure-blue. It is misleadingly called "blue malachite" to distinguish it from "green malachite". It is sometimes used in jewellery in flat-top pieces. Read more.
Baguette
Used in jewellery to describe a rectangular-cut gemstone.
Brilliant cut
A type of diamond cut, typically round with 58 faces. Read more.
Brooch
Also called a pin, an ornament that can be pinned to a garment.
Cabochon
A stone that has a rounded, domed surface with no facets.
Cameo
A relief carving (a carving that comes up above the surface) on a shell or stone. Read more.
Carat
The unit of weight for a diamond or other gemstone and also for a pearl, equivalent to 200 mg.
Standard to define the fineness of gold and gold alloy, expressed as a number out of 24 parts, e.g. "14 carat" means 14/24ths gold in the alloy. 24 carat gold is pure gold. Most jewellery uses gold of 14 of 18 carats. For convenience, the fineness of gold may be expressed in thousandths rather than carats:
- 24 carats = 1,000 thousandths (1.000),
- 18 carats = 750 thousandths (0.750),
- 14 carats = 583 thousandths (0.583),
- 12 carats = 500 thousandths (0.500).
Carbonado
A rare type of opaque black diamond; they are not normally used for jewels, but for items like drilling bits and abrasive wheels.
Cat's eye chrysoberyl
A yellow to green-yellow to grey-green stone with a bright, pupil-like slit that seems to move slightly as the stone is moved. Usually cut as cabochon. Read more.
Chalcedony
A family of minerals that is often milky to grey to bluish in colour.
Chatoyancy
The lustrous, cat's eye effect seen in some cabochon stones, like tiger's eye, and sometimes in other stones, like aquamarine.
Chrysoberyl
A hard stone that ranges in colour from yellow, to brown, to green.
Cluster setting
Setting in which small stones or pearls are set around a larger stone.
Coral
A hard, calcareous organic substance that is the skeleton of certain polyps, small marine invertebrates that live in colonies. The variety used in jewellery is precious coral, which is compact and solid, without visible indentations. The colours shade from pinkish white to pale pink and ok-blood red. It is mainly used as beads or set en cabochon. Read more.
Citrine
Citrine (from the French for "lemon") is a rare, yellow type of quartz, a semi-precious stone that ranges in colour from pale yellow to orange to golden brown. The best quality citrine is found in Brazil. Read more.
Cufflinks
Cufflinks are men's jewellery that closes the buttonholes of the cuff of a long-sleeved shirt. They were first worn in the 1800s.
Cultured pearl
Pearl whose formation is started by human intervention with the insertion a piece of mantle tissue into the oyster or mussel. Read more.
Cushion cuts
The most common shape for old or baroque brilliant-cuts. It has a rectangular or square cross-section, with rounded corners.
Chrome diopside
Chrome diopside is an emerald-green coloured gemstone. It is a chromium-rich variety of the common mineral diopside.
Danburite
A clear to white silicate mineral whose orthorhombic crystals are transparent to translucent (danburite can also be yellow, greenish, or brown); it resembles topaz.
Diamond
Precious, lustrous gemstone made of highly-compressed carbon. Diamonds are one of the hardest materials known. Colours of diamonds range from colourless, yellow, orange, brown, to almost black. Rarer colours are red, blue, green, and purple; these colours (called fancies) are quite valuable. Canary diamonds have a deep yellow colour. A diamond's value is based on the "4 C's": colour, cut, clarity, and carat weight. A diamond's colour (saturation) is rated on an alphabetical scale ranging from D (white) to Y (yellow). "Z" are fancy, or deep-coloured. A diamond's cut is designed to maximize the stone's natural "fire"; brilliant cuts are preferred. A diamond's clarity depends on the number and size of its flaws and inclusions of other minerals, like quartz. Clarity can be rated FI (flawless), IF (flawless at 10x magnification), a series of V ratings (very small flaws at 10x magnification), a series of S ratings (small flaws at 10x magnification), to I1, I2, and I3 (having inclusions visible to the naked eye). Read more.
Emeralds
Very hard, green precious stones. Flaws and cloudiness (called jardin) are very common in emeralds, so many emeralds are oiled, irradiatied, and dyed to improve their look. Synthetic emeralds have fewer imperfections and are very hard to distinguish from natural emeralds. Emeralds belong to the beryl group of stones (which also includes aquamarines, morganite, and chrysoberyl), which have large, perfect, six-sided crystals. Emeralds were long thought to have healing powers, especially for eyesight. Read more.
Emerald cut
A cut that is used for large transparent gemstones, such as diamonds and emeralds, so that the table and the contour of the stone are square or rectangular and the sides are step cut.
Enamel
Vitreous substance, opaque or transparent, that is fired at a high temperature and used to decorate dials, cases, etc. Several successive firings take place in an oven heated up to 840° C. Some techniques date back to ancient China.
Facets
Flat surfaces on a cut stone or glass.
Fancy diamond
Rare diamond of intense colour.
Feldspar
A large group of minerals that is found in a wide area of the earth, but only a few of its members, including moonstone, is suitable for gemstones.
Filigree
A gold or silver wire that has been twisted into patterns and soldered into place. Openwork filigree is not soldered onto a sheet of metal and is difficult to make. Imitation filigree is made of stamped metal.
Flaw
An imperfection in a gemstone. A flawless stone is called a "clean".
Fresh water pearls
Pearls cultivated in molluscs, not oysters, found in fresh warm lakes and rivers. They are generally elongated in shape and have a milky translucent appearance. Their wide range of interesting shapes make up in fashion appeal for their relatively low value. Read more.
Fluorite
Fluorite is a mineral that comes in many colours, including purple, red, pink, yellow, green, blue, black, and multi-coloured stones. Crystals are transparent to translucent. Fluorite is in many parts of the world.
Garnet
Any of a group of semi-precious silicate stones that range in colour from red to green (garnets occur in all colours but blue). Some garnets used as gemstones include pyrope (the deep red garnet), almandine, spessartine, grossular, the iron-aluminum dark red garnet (also known as the carbuncle stone), uvarovite (rare), and the lustrous andradite (which includes the valuable green demantoid garnet, topazolite, and melanite). Read more.
Gold
A precious metal that is very soft when pure (24 Kt.). Gold is the most malleable and ductile (able to be made into wire) metal. Gold is alloyed (mixed with other metals, usually silver and copper) to make it less expensive and harder. The purity of gold jewellery is measured in carats.
Guilloché
A style of engraved decoration on metal achieved by an engine-turning lathe with an eccentric motion that can cut a variety of patterns.
Hallmark
Symbol stamped in metal to guarantee the origin and content of precious metal.
Iridescent
An object that displays many lustrous, changing colours. Iridescence is caused by the reflection of light from the jewel.
Jade (Jadeite)
A semi-precious stone that ranges in colour from green to white to lilac to brown to almost black. Translucent jade is more highly valued than opaque jade. Jade is often cabochon set. Stones with imperfections are usually carved (the imperfections are simply carved away). Two different minerals are known as jade: jadeite and nephrite. Jadeite is the harder of the two; it is usually used in jewellery production. Nephrite is slightly softer and is often veined; it is used in carvings, for making beautiful bowls and vases. The Chinese have prized jade for thousands of years and regarded it as having medicinal properties when worn or ingested as a powder. Read more.
Keshi pearl
From Japanese for "poppy", a keshi is a relatively small pearl formed naturally in the oysters or molluscs that produce cultured pearls. The tiniest, at one to three millimetres in diameter, are dubbed "poppy" or "seed" pearls. Read more.
Kunzite
A transparent pink, light pink or light purple gemstone that resembles rose quartz. It is a variety of the mineral spodumene. Kunzite can fade after prolonged exposure to light. Kunzite is also called "evening stone," because of its propensity to fade in bright light. The original colour of some kunzite stones can be restored or even intensified by irradiation. It is usually used as a large stone and is easily chipped; small stones of kunzite are difficult to cut. Read more.
Kyanite
A deep sapphire blue, green, grey, or white gemstone. The colour is not always uniform; it can be blotchy or in streaks.
Labradorite
Is a fairly abundant greyish mineral that has brilliant flashes of colour (usually green, blue or red) after it is polished (called labradorescence). The crystals are transparent to translucent. There is a darker variety of labradorite (called "black moonstone") which has bluish inclusions. Labradorite is usually cut with a flat surface in order to highlight the flashes of colour. Labradorite was originally found along the coast of Labrador; it is also found in Newfoundland and other parts of Canada.
Lapidary
A craftsman who cuts and polishes gemstones.
Lustre
A property related to the reflectivity of light on a mineral's surface.
Malleable
Capable of being easily shaped or formed, malleable metals can be worked with a hammer or a roller. Gold and sterling silver are very malleable metals.
Malachite
An opaque semi-precious stone with layers of deep green and light green, usually found in copper mines. Read more.
Marquise
A cut that gives precious stones a shape like an oval with two pointed ends.
Mineral
A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystalline structure, color, and hardness. Examples of minerals include: A substance, such as stone, sand, salt, or coal, that is extracted or obtained from the ground or water and used in economic activities.
Mohs scale
The Mohs Scale measures a substance's hardness, that is, how resistant it is to being scratched. In the Mohs Scale, which ranges from 1 to 10, one substance is harder than another if it can scratch it. For example, a diamond (hardness = 10) will scratch garnet (hardness = 6.5-7.5), but not the other way around.
Micron
Metric unit of length, equivalent to one thousandth of a millimetre and represented by the symbol µ. In the watch industry, tolerances are often expressed in microns.
Mother-of-pearl
The iridescent coating on the inside of oyster shells. Mother-of-pearl is used for jewellery, buttons, among things.
Moldavite
A rare, glassy, translucent, dark green gemstone. Moldavite is a silica-based tektite, a mineral formed when a meteorite (a rock from space) struck the Earth's surface and melted, fusing the surrounding rock. Moldavite is only found in Bohemia (the Czech Republic).
Mollusc
An aquatic, soft-bodies invertebrate that lives in a shell, found either in seawater or freshwater. If it has only one shell (e.g. the abalone shell), it is "univalve". If it has two shells connected by a hinge, it is an oyster or "bivalve" mollusc.
Moonstone
A variety of feldspar that is transparent or translucent. Moonstone has been imitated in glass.
Obsidian
A volcanic glass (also called Apache tears) that is usually black, but occasionally red, brown, grey, green (rare), dark with "snowflakes," or even clear. This glassy, lustrous mineral is found in lava flows, and obsidian stones can be massive. Obsidian is formed when viscous lava from volcanoes cools rapidly. Most obsidian is 70 percent silica.
Onyx
A semi-precious stone that is black and white, generally arranged in layers. It is a form of agate with parallel banding. Onyx is a species of chalcedony.
Opals
Semi-precious stones that are luminous and iridescent, frequently with inclusions of many colours ("fire"). Opal is a mineral composed of noncrystalline (amorphous) silica water, and is a species of quartz. There are three major types of opals: common opal, opalescent precious opal (white or black, with a rainbow-like iridescence caused by tiny crystals of cristobalite), and fire opal (a milky stone that is orange to red in colour with no opalescence). Read more.
Opalescence
A milky white/blue type of iridescence.
Orient
The deep, inner glow and shimmering iridescent characteristics of sea-grown pearls. The deeper the lustre and iridescence, the more precious the pearl.
Paved
Term used to describe a particular kind of decoration; for example, on dials in which precious stones, such as brilliants and pearls, are set next to each other without any apparent space between them.
Pear cut
A teardrop shaped gemstone used for pendants, drop earrings and other pieces of jewellery.
Pearl
Organic gems grown within oysters and abalones, formed when a foreign object (like a tiny stone) has made its way into the mollusc's shell. The mollusc secretes nacre, a lustrous substance, and as thousands of layers of nacre coat the intruder, a pearl is formed. This process takes up to seven or eight years. The most valuable pearls are perfectly symmetrical, large, naturally produced, and have a shimmering iridescence. Pearls may be natural or cultured (i.e. when the irritant is purposely placed in the oyster's body). Read more.
Pendant
Hanging ornament, often used with necklaces, pins and earrings.
Platinum
A valuable, rare metallic element that is very heavy, silvery-white, non- corroding and malleable. As its price exceeds that of gold, it is used in jewellery only for fine articles, but in the form of platinum alloy.
Princess cut
A square-cut stone. It is a relatively new cut and is also known as a quadrillion or squarillion cut.
Refraction
A change in the velocity and direction of a light ray. In diamonds, the carbon atoms are so compact that light decelerates dramatically when it enters the stone. This allows a correctly-cut stone to reflect light and display the gem's characteristic brilliance.
Rhodochrosite
A mineral whose colour ranges from rose to pink to almost yellow or brown. Although it is very pretty, this stone is soft and brittle; it is used in jewellery and for carvings and figurines.
Ruby
A precious stone that is a red variety of a transparent corundum, a mineral that is second only to a diamond in hardness. Read more.
Sapphire
A precious gemstone that ranges in colour from blue to pink, to yellow to green to a variety of other colours. Sapphires are related to rubies and are often heat treated to improve their colours. Read more.
Silver
A metallic element that is medium heavy and malleable. It is usually used in an alloy with copper to make it harder.
Stainless steel
Corrosion resistant steel of a wide variety, but always containing a high percentage of chromium. Stainless steel is highly resistant to corrosion attack by organic acids, weak mineral acids and atmospheric oxidation.
Step cut
A style of cutting a large diamond so that, below the table, there are a number of slopping, parallel rows of four sided facets that increase in size.
Table
The large, flat area at the top of a cut gemstone.
Tahitian pearl
These are dark-coloured pearls (also called black pearls). They are produced by the large, black-lipped pearl oyster Pinctada margaritifera (also called the Tahitian black pearl oyster), a mollusc found in the tropical Indo-Pacific Ocean. Black pearls come in many colours, including many body shades and overtone tints including grey (light grey to almost black), peacock green (especially valuable), aubergine (eggplant), and deep brown. The colour of the dark nacre is determined by the minerals in the oyster's diet (plankton) and in its environment. Many "black pearls" are dyed or irradiated to enhance or change their colour; it is difficult to tell a natural pearl from a treated pearl. Read more.
Tanzanite
A valuable, transparent, blue-violet type of zoisite resembling sapphire. It is often heat-treated in order to produce a deeper blue-violet colour. Read more.
Tiger's eye
A yellowish-brown to reddish-brown gemstone that has a silky lustre. The gemstone has bands of yellow and brown; when viewed from the opposite direction, the colours are reversed. Usually set as a cabochon. Read more.
Titanium
A metallic element that has been used mainly in industry because of its lightness, strength and high melting point, but has in recent years been used in some jewellery, owing to the attractive range of colours that it acquires by being heated.
Tourmaline
A dichroic gemstone that comes in many, many different colours; it also appears to have different colours depending on the angle at which it is seen. Tourmaline has the greatest colour range of any gemstone - the lighter colours are more valuable than the darker colours. It ranges in colour from pink to green to red (rubellite) to purple to blue-green (indicolite) to colourless (achroite) to black. Watermelon tourmaline is both pink and green. Tourmaline occurs as an elongate three-sided prism and is mined in Brazil, The Ural mountains in Russia, Namibia, Sri Lanka, and California. Read more.
Translucent
Semi-transparent.
Turquoise
A non-translucent, porous semi-precious stone that is usually cut as a cabochon.
Yellow gold
Gold that has been alloyed with a mix of 50% copper and 50% silver.
Zircon
A lustrous gemstone that comes in colours ranging from golden brown to red to violet to blue. Pure zircon is colourless, but most zircon stones are brown. Zircon stones can be heat-treated to become blue or colourless; sometimes, heat-treated stones revert to their original colour. Read more.
Zoisite
A grey-green mineral that occurs in cracks of igneous rock.
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