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Definitions [M-R]

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Malachite
Malachite is an opaque semi-precious stone with very deep and light green layers, sometimes with thick veins of black running right through it. Malachite is often coated in a colourless wax, oil or hardening agent to enhance appearance and increase durability. The main source for Malachite is the copper mines of the Democratic Republic of Congo, Zambia, Mexico, New South Wales, Israel and Australia. In Israel, Malachite is mined in the Timna Valley which is also known as King Solomon's mines.
Malachite has a Mohs hardnessrating of 3.5 - 4.

Marcasite
Marcasite ('fool's gold') is a mineral that is sometimes referred to as 'white iron pyrite'. It can often be mistaken for Pyrite, but Marcasite is lighter in colour and more brittle. One famous source of Marcasite is Dover in the UK. Marcasite has a Mohs hardnessrating of 6- 6.5.

Mineral
A mineral is a solid material which is formed as a result of a naturally occurring geological process in the earth's crust. To be classified as a mineral it must be solid and posses a crystal structure. A good example of a crystal mineral is a Diamond. The physical hardness of a mineral is measured according to the Mohsscale.

Morganite
Morganite is a member of the Berylfamily. Its colour ranges from pale pink to a hint of Orange. Inferior qualities of the stone can be improved by heating them to 4000°C.
The main deposits of Morganite are in Brazil, Madagascar, Afghanistan and California. It was named after the financier and mineral collector John Piermont Morgan. Morganite has a Mohs hardnessrating of 7.5 - 8

Mohs Scale
In the case of minerals and Gemstones, hardness refers first to scratch hardness then to cutting resistance of each mineral. Friedrich Mohs introduced the term 'Scratch Hardness'. The following table shows the scale that he developed which is still in use today.

The Scale
Diamond 10
Ruby, Sapphire 9
Chrysoberyl 8.5
Spinel, Topaz 8
Aquamarine, Emerald 7-8
Zircon 7.5
Tourmaline 7-7.5
Garnet 6.5-7.5
Amethyst, Chalcedony, Quartz, 7
Steel (pocket knife) 7
Jade 6.5-7
Peridot 6.5
Moonstone 6-6.5
Opal 5.5-6.5
Turquoise 5-6
Lapis lazuli 5-5.5
Glass 5
Iron 4
Azurite 3.5-4
Bronze, Coral, Pearl 3
Gold 2-3
Amber, Fingernail, Ivory,
Shell, Jet 2.5
Talc 1

Mollusk
The word Mollusk describes many varieties of Shell Fish, some of which can naturally produce Pearls and the Mother of PearlShell.

Moonstone
Moonstone is a semi-translucent stone, which can appear in several colours. It is usually whitish- blue; however it can be found in grey, orange, and red and sometimes even appear with no colour at all. Deposits of Moonstone can be found in the following countries; Mexico, Tanzania, Myanmar, Madagascar and Sri Lanka. It can also be found in the USA, specifically Pennsylvania and Virginia. The stones of the best quality are found in Sri Lanka. Labradorite and Albite are rare forms of the stone. Moonstone has a Mohs hardnessrating of 6.

Mother of Pearl
'Nacre' is another name for Mother of Pearl. Mother of Pearl is an organic material produced by some Mollusks on the inner layer of their shells. This material is very strong, resilient and iridescent. It has many uses from jewelry to pistol handles. The main sources of Mother of Pearl are the warmer waters of Asia. The freshwater water variety can be found in many rivers across the USA, Europe and Asia. Mother of Pearl has a Mohs hardnessrating of 3.
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Necklace
A necklace is a piece of jewelry worn around the neck. Necklaces of different lengths have different names: A choker is 14" to 16" long; a princess necklace is 18" long, a matinee necklace is 22" to 23" long, opera is 30" to 35" long, and a rope is over 40" long.

Nephrite
Nephrite is an ornamental stone that can be used in carvings, beads and cabochon cut gemstones. It can be found in many colours; Blacks, reds, pinks, violets. Nephrite jade was once believed to be a cure for kidney stones and was used pre 1800 by the Chinese. It can be located in New Zealand other deposits are in Australia, Brazil, China, Canada, Russia, and Zimbabwe. Nephrite has a Mohs hardnessrating of 6 to 6.5.
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Obsidian
Obsidian was named after the Roman, Obsius. It has also been referred to as 'Apache Tears'. Obsidian is volcanic glass that is usually black in colour; however it can also form in red, brown, grey and even green - which is very rare. This glass-like lustrous mineral forms in fiery volcanic rock lava flow. Obsidian can form in very large sizes. It has a Mohs hardnessrating of 5.

Onyx
Onyx comes from the same Greek word which translates to nail or claw. Onyx is a member of the Chalcedony quartz family. Its colour is usually black or white. This stone was very popular with the ancient Greeks and Romans. Onyx has a Mohs hardnessrating of 7.

Opal
The word opal derives from the Sanskrit word ôupalaö which means 'Valuable Stone'. Opals are divided into 3 subgroups: Precious Opals, Fire Opals and Common Opals. Their physical properties vary considerably. Precious Opal's special characteristics are its play of colour. It displays rainbow-like colours that can be seen right through the stone - especially in round cut stones. Types of Precious Opals are as follows: White Opal, Black Opal, Opal Matrix, Boulder Opal, Harlequin Opal, Jelly Opal and Crystal Opal.
Fire Opal, named after its orange colour, is usually milky in appearance. However, its best qualities can be clear and transparent which are suitable for faceting.
Common Opal is opaque and rarely translucent. It shows no play in the colour and has a wide range of trade names: Agate Opal, Angel Skin Opal, Wood Opal, Honey Opal, Hyalite, Hydrophane, Porcelain Opal, Moss Opal, Girasol, Prase Opal, and Wax Opal.
In order to display the stone's best qualities, it must be polished and cut in to round or oval cabochans. Opal has a high water content; sometimes as high as 10%. If the stone becomes dry, it can become brittle and cracks may start to appear. The colour will also appear to fade. For this reason, Opal must be worn by the owner as often as possible so the stone will receive the required amount of air and humidity. The best way to store Opal is to place it in damp cotton wool.
Almost 95% of the world's Precious Opal originates from Australia. Deposits of Fire Opal can be found in Brazil, Mexico, Guatemala and the USA. The Mohs hardnessrating for Opal is 5.5 to 6.5.

Opaque
Opaque means blocking the passage of light as opposed to translucentor transparent.

Oxidisation
This blackening of certain metals is a natural chemical reaction and occurs when exposed to oxygen. This effect can also be induced by chemicals.
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Pavè setting
A pavè setting is where small stones are set as close as possible, so that the piece literally looks like it has been 'paved' with stones.

Pearl
There are many types of pearls, including natural pearls, (made with no human interference), Cultured Pearls, pearls made by inserting a small piece of foreign tissue living oyster or Mollusk. Baroque pearls, irregularly- shaped pearls, freshwater pearls, seed pearls and Biwa pearls are pearls that are formed in the freshwater mussel. The Mohs hardnessrating for a pearl is 3.

Pendant
A pendant is an ornament that usually hangs from a chain/collar/cord which is worn around the neck. Pendants can be made from many different materials: from Diamondsto plastic.

Pewter
Pewter is a metal alloy that is composed mostly of tin and combined with lead, antimony, bismuth, copper, and/or silver: the formulation varies quite a bit. When pewter is polished it has a silvery luster. Pewter is a soft alloy, with over 90% tin content.

Peridot
Peridot can also be referred to as 'Olivine' it has a vivid green colour which is a perfect colour to be worn in the summer months. This stone can be found in abundant quantities in Pakistan and Afghanistan. The largest cut Peridot weighed 319 carats and was found on the Island of Zabargad. Peridot has Mohs hardnessrating of 6.5 .

Platinum
Platinum is a white coloured precious metal that is very strong and dense. Jewellery made from Platinum is usually 90-95% pure metal. Platinum is 60% heavier than gold, it wasn't discovered until the 1700's in Russia. To increase the strength and workability of the metal it is alloyed with Ruthenium, Palladium, Iridium and Osmium which are all members of the Platinum family.

Porous
A porous material is a solid object filled with pores or gaps. These gaps can become filled with either a liquid or a gas. There are many examples of porous materials in the world today; bones, cement and foam to name just a few. Porous Gemstones can be injected with colour to give them a more vibrant colourful finish.
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Quadrillion Cut
A Quadrillion cut stone is square cut stone. This fancy cut is relatively new and is also known as a Princess or Squarillion cut.

Quartz
Quartz is a crystalline mineral that comes in many forms, including Amethyst, Aventurine, Citrine, Opal, Rock Crystal, Tiger's Eye, Rose Quartz, with many others under the heading Quartz. Rutilated Quartz and Tourmalinated Quartz have needle-like occlusions of other minerals. These occlusions can enhance the appearance dramatically. This common mineral is found right around the globe. From Brazil to India, California to South Africa. Quartz has a Mohs hardnessrating of 7.0 .
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Rhinestones
Rhinestones are highly reflective glass pieces cut and polished (faceted) to imitate gemstones. The original rhinestones were quartz stones (rock crystal). The best made rhinestones today are formed from highly reflective leaded glass which is cut and polished. Rhinestones were initially sourced from the Rhine River. Rock crystal has Mohs hardnessrating of 7.

Rhodium
Rhodium is a white precious metal that is quite expensive. Rhodium is often used in the plating of base & precious metals to give it a Platinum-like sheen. The main source of this alloy is South Africa.

Rhodolite
Rhodolite (which means 'Rose Stone' in Greek), is a member of the Garnet family. It has a colour range from purple-red to pink-red. The main deposits of the stone are Sri Lanka, Zimbabwe, Kenya and the USA. Rhodolite has a Mohs hardnessrating of 7 to 7.5.

Rhodonite
Named after the Greek word for rose, it is a reddish-pink colour with thin veins or patches of gray to black. In the past, Rhodonite has also been used as an ornamental stone. It can be found in the former Soviet Union, the U.S., India, and Australia. The Mohs hardnessrating is 5.5 to 6.5.

Rhodochrosite
Rhodochrosite (Greek: 'rose coloured') has only been on the market since the 1940's. It's a very pretty stone to look at; however it is very soft and very brittle. It has, in the past, been used for jewellery, ornaments and figurines. Transparent crystals are very rare and sought after by collectors. The most important deposits are in Argentina. Other significant deposits can be found in Peru, Germany, Mexico, South Africa, Russia, Italy, the USA, and Romania. Rhodochrosite has a Mohs hardnessrating of 3.5 to 4.

Ring
A ring is a piece of jewelry worn around the finger; rings can be worn on any finger, including the thumb. Rings have been worn throughout the ages, and often have significant meaning. Some rings include wedding and engagement rings (denoting commitment), rings denoting group membership (like Masonic rings or college rings), and devotional rings (with religious meaning). Rings come in just about any size you need (some larger rings will have to be specially made) and they can be made from many different alloys, plastics and stones.

Rock Crystal
This is one of the most common minerals of the earth's crust. The name crystal comes from the Greek for 'ice'. It was believed that Rock Crystal was eternally frozen. Rock Crystal weighting many, many kilograms has been found. However, cuttable material is rare. Important deposits have been found in Brazil, Madagascar, the USA, and the Alps. They are often used for costume jewellery and delicate ornaments to imitate Diamonds. It can be confused with many colourless gems as well as glass. Rock Crystal has a Mohs hardnessrating of 7.

Rose Quartz
Rose Quartz is named after its pink colour. It's a form of quartz that can have traces of rutile needles which can cause a Six-Rayed star (asterism) when cut into cabuchon. Deposits are found in Brazil and Madagascar as well as India, Namibia and Sri Lanka. Only larger stones can be faceted. Rose Quartz can be mistaken for Kunzite. Rose Quartz has a Mohs hardnessrating of 7.

Ruby
Rubies are a very precious member of the Corundum family. The colour range is a deep red to purple/brown. The most sought after colour of the stone is what has been referred to as 'Pigeons Blood'. ItÆs a pure red colour with a hint of blue. As a rough stone, Ruby appears dull and greasy. However, when cut and polished, the lustre can come close to that of a Diamond. Just like Emeralds, occlusions in the stone can identify its authenticity. During the renaissance period Rubies were thought to have the power to counteract poison. The world's largest Ruby is known as the Raviratna it weights a whopping 3600 carats. Some of the most important deposits are in Burma, Thailand and Tanzania with only one percent of the rubies mined in these areas are of a gemstone quality. Rubies are a very hard gemstone with only Diamonds being superior. Rubies have a Mohs hardnessrating of 9.

Rutilated Quartz
Rutilated quartz is a type of rock crystal which contains long, fine needles of rutile crystals (titanium dioxide). This beautiful stone is usually cut as a cabochon. It is also known as Venus' Hair Stone, Cupid's darts, and Fleches d'amour (arrows of love). Rutilated Quartz has a Mohs hardnessrating of 7.
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