Gemstone Glossary
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Agate
A form of chalcedony which forms from layers of quartz usually showing varicoloured bands. It usually occurs as rounded nodules or veins. The composition of agate varies greatly, but silica is always predominant, usually with alumina and oxide of iron.

Amber
A fossilized resin from pine trees. Amber deposits have been found that are over 150 million years old, but most amber used in jewellery or ornamentals is between 20-90 million years old. As the sticky resin oozed from ancient pine trees, small insects, plant material, feathers and other small objects in the path of the flow became entrapped. Over time, the resin was encased in dirt and debris and through a process of heat and pressure it fossilized to become amber. Amber exhibits a resinous lustre.

Amethyst
The purple variety of quartz. Although it must always be purple to be amethyst, it can and does have a wide range of purple shades including purple, lilac and mauve. The most expensive amethyst is a deep purple, but today, most amethyst is heat treated to produce a deeper colour. Amethyst is found in geodes and alluvial deposits all over the world and occurs in both crystalline or massive forms. It is a 7 on the Mohs scale of hardness.

Aquamarine
The aquamarine is a member of the beryl family and ranges in colour from a pale almost colourless blue to blue-green to pure blue. Some of these stones are heated to enhance their colour and change a light coloured stone to pure blue. Legend tells of sailors who wore aquamarines to keep them safe and to prevent seasickness. The most valuable aquamarines come from Brazil.

Beryl
Occurs in a variety of colours including green, yellow, greenish-yellow, blue to blue-green, red, colourless and pink. The name is from ancient Greek, beryllos, and means "precious blue-green colour". There are extensive references to beryl as a gemstone in folk lore.

Birthstone
A rock or gemstone associated with the calendar month of birth or a sign of the Zodiac. The origin of birthstones is said to be based on the Breastplate of Aaron which is described in Exodus 28, 15-30. Instructions for fabricating the Breastplate called for the twelve stones of the Twelve Tribes of Israel to be set in four rows. These gemstones corresponded to the zodiac signs of the time.

Bloodstone
A soft green jasper mottled with red spots from iron oxide. A type of chalcedony, it is also known as Heliotrope. Bloodstone is a relatively soft stone and is one of the ancient birthstones for February or March.

Carat (ct.)
The standard measure of weight used for gemstones. One carat weighs 0.2 gram (1/5 of a gram or 0.0007 ounce). A hundredth of a carat is called a point.

Chalcedony
Pronounced ‘kal-sed-uh-nee’, is a micro crystalline member of the quartz family. It is found all over the world and is one of the oldest stones used by humans for decoration. It has a waxy lustre and may be opaque as in jasper, petrified wood, and bloodstone or translucent to transparent in agate, carnelian, or chrysoprase. In the jewellery trade, the term chalcedony usually refers to white, grey, or blue translucent stones such as "Blue Chalcedony".
Other forms of chalcedony are onyx, sard, sardonyx, petrified dinosaur bone, chert, flint, fire agate and dendritic agate. Because it is a porous stone, it can be stained or dyed to enhance or change the natural colour of the stone. Agates are often dyed while most onyx used for jewellery purposes is dyed black, thus the name "black onyx".

Charoite
A fairly recent discovery found in Russia in 1978 in the Murun mountains in Yakutia, near the Charo River. This is the only known location for this rare mineral. It ranges in colour from a light lilac to a deep purple and can be mottled with grey, white and black inclusions. The chatoyant variety in a bright deep purple, is usually considered more valuable than the non-chatoyant variety although both are used in jewellery and compliment a number of other stones.

Chatoyant
This term is applicable to a number of different stones. Tiger's Eye is one example. A chatoyant gem exhibits a changeable silky lustre as light is reflected within the thin, parallel, fibrous bands. This effect is due to the fibrous structure of the material. (pronounced: cha-toy-ant).

Cubic Zirconia
A man-made, synthetic stone used as an inexpensive alternative to a diamond or other coloured stone.

Emerald
The green member of the beryl family. Traces of chromium and vanadium in the crystalline structure are what produce the green colour. These gemstones were mined by the Egyptian Pharaohs as early as 3000 B.C. and the ancient Incas and Aztecs of South America regarded them as holy. Today, the best and most valued, stones come from Colombia. Mohs hardness 7.5 - 8.

Garnet
Garnets occur in every colour except blue and most varieties are named for their colour. Rhodolite is a purplish red, hessonite is the name for an orange, cinnamon, or pinkish variety. Tsavorite is the name given to dark green grossularite. Uvarovite and demantoid are also green varieties.

Gemstone
The common definition of a gemstone is any precious or semi-precious stone, rock or mineral.

Hardness
A substance's hardness value indicates the materials resistance to scratching and grades minerals on a comparative scale from 1 (very soft) to 10 (very hard). In the Mohs scale of Hardness, a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower rating. The Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773-1839) in 1812.

Inclusion
In gemstones, an inclusion is any solid, liquid, or gaseous foreign body enclosed in the mineral or rock.

Jade
An opaque, semiprecious stone found in shades of green, light purple, yellow, pink and creamy white shades. The term jade is often used to describe both jadeite and nephrite which are similar in appearance and use. The best quality jade comes from Myanmar (formerly Burma). Jade is not only a hard stone, 6.5 to 7 on the Mohs scale, but is also an extremely tough stone which allows it to be cut as a solid piece and used for a ring or bracelet.

Jasper
An opaque and fine grained variety of chalcedony quartz. It is found all over the world in all colours including: red, brown, pink, yellow, green, grey/white and shades of blue and purple and is often spotted (dalmation), striped (banded jasper), and/or multi coloured (picture jasper, poppy jasper).

Lustre
A stone's lustre is its glow or sheen, the result of the way it reflects light. Lustre is dependent on both the stone's surface (polish) and the reflective index of the mineral. Experts use many terms to describe lustre: adamantine, pearly, greasy, metallic, silky, resinous, vitreous, earthy or dull, and waxy.

Onyx
A variety of chalcedony quartz, often with parallel banding. When chalcedony is variegated it is called agate. Black onyx may be opaque or translucent and although it does occur naturally in black, it is usually dyed to darken its colour. White onyx is a semi translucent white to whitish-yellow stone that was often used in Victorian jewellery for cameos. It has a hardness of between 6.5- 7 on the Mohs scale.
Natural black onyx is a brittle stone requiring care during cutting or carving.
Originally, almost all colours of chalcedony from white to dark brown and black were called onyx. Today when we think of onyx we often preface the word with black to distinguish it from other varieties of onyx that come in white, reddish brown, brown and banded. A variety of onyx that is reddish brown with white and lighter reddish bands is known as sardonyx.

Opal
Most opal is 50-65 million years old, dating back to the time of dinosaurs in the Cretaceous period. Opal formed as silica from decomposing rocks that mixed with ground water and formed a silica gel that hardened in underground cavities and fissures. There are two distinct types of opal, common and precious. The way the silica particles form determines which type. In precious opal, silica particles are packed in regular rows and layers. Moving the stone causes light to diffract, or split, as it grazes the opal surface. This light diffusion shows iridescent flashes of green, blue, aqua and sometimes yellowish or red colours which are referred to as "fire". Opal is found in a wide range of colours including: green, blue, aqua, and pink.

Opaque
An opaque gem is one that does not allow light to pass through it, is not transparent or translucent.

Pearly
The term used to describe the surface of a gemstone which exhibits a lustre similar to that of a pearl or mica.

Precious Gemstone
Diamond, ruby, sapphire, emerald and precious opal are the precious stones. Any other rock or mineral is referred to as semiprecious.

Quartz
Quartz is the most common mineral on earth. It is a crystalline mineral that comes in many forms.

Resinous
A type of lustre exhibited on gemstones like amber.

Ruby
Ruby is one of the four precious gemstones along with Diamonds, Emeralds and Sapphires. Ruby is a member of the corundum family whose colour comes from chromium oxide in the stone. Although corundum can come in many colours, rubies are, by definition, red. Rubies are extremely hard; only diamonds are harder.

Sapphire
Sapphire is one of the four precious gemstones, along with Diamonds, Emeralds and Rubies. Sapphire is a member of the corundum family which come in a variety of colours.

Sardonyx
A banded variety of chalcedony characterized by parallel bands of brownish red sard and white translucent onyx. It is also used for intaglios and cameos. While sardonyx is found naturally in bands of brown, brownish-red and white, much of that found on the market today is actually dyed agate.

Sardonyx
Sardonyx is a variety of onyx, consisting of alternating layers of sard and white chalcedony.

Semiprecious
Semiprecious refers to any gemstones valued for their beauty but which are not one of the four "precious stones", (diamond, ruby, sapphire or emerald).

Spinel
Spinel is probably named from the Latin word "spina", (meaning "thorn"), for its pointed crystals. Spinel is a hard mineral with octahedral crystals occurring in igneous and carbonate rocks. It is found in a variety of colours including blue, green, brown, black, and the valuable red variety which resembles a ruby.

Synthetic
Synthetic gemstones are produced in a laboratory rather than found in nature. Synthetic gemstones are not "fake", since they have exactly the same chemical characteristics as the natural stone, but they are usually flawless and much cheaper than the real thing. The most common synthetic gems are ruby, sapphire, emerald and opal.

Topaz
Topaz is a hard stone, but topaz can be susceptible to breaking. The name is from Topazos, a small island in the Red Sea, where the Romans obtained a stone which they called by this name, but which is now called chrysolite. It may be found in many colours, such as blue, brown, clear, green, orange, pink, red, yellow and white. The most valuable topaz is "Imperial" topaz with a golden yellow to orange colour. The most popular colour is an enhanced blue treated with heat to develop it into a rich “Tiffany” blue colour which resembles aquamarine, but is more affordable.

Tourmaline
Tourmaline is a complex crystalline silicate. Black tourmaline (schorl) is the most common variety, but there are also other varieties, as the blue (indicolite), red (rubellite), also green, brown, and white. The red and green varieties when transparent are valued as gems. Tourmaline can be found in more colours than any other stone and heat can also be applied to tourmalines to lighten, or enhance, the existing hue of the gem.

Translucent
As a jewellery term, this applies to a gemstone that allows light to pass through the stone but with enough diffusion to prevent the ability to see distinct images through the stone. A moonstone is a translucent stone.

Transparent
Used to describe stones that are clear and transmit light so that objects can be seen through the stone. Many fine quality coloured stones such as ruby, citrine, or topaz are transparent. However, due to the depth of colour or inclusions, you may not be able to discern an exact representation of the object as you would if looking through a transparent window glass. Quartz is another example of a transparent stone, it may be as clear as a window pane and was sometimes used as such in early times.

Turquoise
Turquoise is coloured by copper salts found in desert regions throughout the world. Different colours of turquoise, varying from sky blue to nearly green occur in untreated turquoise. Interesting matrix patterns are considered to add beauty to the stone. Only Persian turquoise is usually without apparent matrix. Modern turquoise stones that appear very shiny and absolutely flawless are actually manufactured. Touching the stone leaves oils on it, which alters the colour of the turquoise over many years. Collectors tend to value these colour nuances as "the patina of time". Turquoise is usually cut into cabochons, or domes, to enhance its natural beauty.

Ultrasonic cleaner
An ultrasonic cleaner is a machine that cleans jewelery by using a fluid that is vibrated at 20,000 cycles per second. When the vibration speed rises above the ultrasonic frequency level, bubbles explode and generate strong power, cleaning the surfaces and cavities of hard-to-clean objects. Ultrasonic cleaning does not scratch the surface or harm objects like many chemical or abrasive cleansers.

Zircon
Zircon is a common mineral occurring in small crystals which is heated, cut, and polished to form a brilliant blue-white gem used as a refractory when opaque and as a gemstone when transparent. They are not man made stones like cubic zirconia are. Although they are frequently colour-treated, zircons occur naturally in clear, yellow, orange, brown and red. They are a chief source of zirconium.

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