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Friday, 16.11.2018, 18:14

Evriviadis Kosmimata

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Amber is fossilised tree sap formed millions of years ago and discovered along the Baltic Sea by Stone Age people. Because it is an organic gem -- one formed from living organisms -- amber can contain suspended fragments of animals or plants, making it a true time capsule! Most of us think of a lustrous reddish gold hue when we think of amber, but it comes in shades ranging from whites and yellows to reds and browns; its former prevalence along the Baltic coast of Germany, Poland and Russia earned it the name "gold of the North." Today's major source of amber is the Dominican Republic.

Amethyst is a variety of quartz, is an abundant gem that comes in a range of shades from pale lilac to deep purple. Because it is so plentiful, amethyst is also affordable; still, its rich, lush purple -- the colour of royalty -- has long made it a prized gem in coronation regalia, from the ancient Greeks and Romans to British royal families. South America, particularly Brazil, is today's major source of amethyst.

Aquamarine whose name comes from the Latin for "sea water," is a member of the beryl family. Aquamarine crystals usually have excellent clarity, can grow to very large sizes and range in colour from greenish blue to light blue-green. Most aquamarine is heat-treated to remove traces of yellow and intensify its rich blue colour. Brazil is today's major source of aquamarine.

Blue Topaz is a magnificent gem to include in any collection. Before the 1950s, topaz was more commonly associated with a yellow or golden gemstone, but with improved treatment processes, the blue topaz has become one of the most popular and widely used of all gemstones! Part of its popularity comes from it's affordability, especially when compared to the cost of other blue gems like the aquamarine and the sapphire. Another wonderful quality about the blue topaz is the impressive range of brilliant blues it comes in. The lightest blue topaz gems are often referred to as Sky blue topaz, the more pastel gemstones may be called Swiss blue topaz while the most intense, darkest gems are commonly named London blue topaz. This plentiful gem is currently found throughout the world including Brazil, Sri Lanka, Mexico and the United States.

Chalcedony is an opaque bluish-white gemstone that is actually a member of the largest family of minerals on earth -- the quartz family. Chalcedony, known scientifically as microcrystalline or cryptocrystalline, is a variety of quartz made up of finely grained microcrystals too small to be seen by the naked eye. There are hundreds of different chalcedony varieties that come in an amazing range of colours and patterns. In the gem trade, the name chalcedony describes only white or lightly coloured gemstones with a waxy lustre. Collectors and gem dealers call all other varieties of chalcedony by their particular name. Some of the more popular varieties include agate, bloodstone (or heliotrope), carnelian, chrysoprase, jasper, moss agate, onyx, plasma, sard and sardonyx. Because of its abundance, durability and beauty, chalcedony was one of the earliest raw materials used by humans in both practical and ornamental forms. World-wide, there are literally thousands of localities where fine specimens of chalcedony have been found. Just a few of these places include Uruguay, Brazil, south-western Africa, and the Lake Superior area in the United States and Canada.

Citrine is a variety of quartz, is popular for its warm yellow to orange colours and its affordable pricing. Another one of citrine's assets is its wide range of sizes -- citrines in 20-carat sizes are not uncommon! Citrine's versatility and wearability make it a popular choice for jewellery, either used alone or combined with diamonds or other gems. Before the development of modern mineralogy, at a time when gems were identified by colour, Citrine was often mistaken for the similarly coloured topaz. Its name derives from the Latin word citrus, meaning "citron." Almost all Citrine is heat-treated to enhance its colour. Today's sources of Citrine are Bolivia, Brazil and Spain.

Emerald is the most famous member of the beryl family, is prized for its lush green colour Known as one of the "Big Three" along with sapphire and ruby, emerald's name derives from smaragdus, the ancient Greek word for "green." Most emeralds have natural birthmarks (fissures or inclusions); because of this, they are routinely treated by a process called "oiling," which means filling fractures that reach the surface with colourless oils or resins to improve an emerald's clarity and colour. Colombia is one of the world's largest commercial producers of emeralds; Colombian emeralds are highly valued for their excellent colour. Other sources include Zambia, Zimbabwe, Afghanistan, Pakistan, Brazil and Russia.

Garnet is actually the group name of a gemstone. Named granatus or "seed," by the Romans because of the stones' resemblance to pomegranate seeds, garnets come in a wide range of colours, except blue. Pyrope, from the Greek word pyropos ("fiery-eyed"), ranges from medium to dark reddish orange to purplish red; the most prized pyrope colour is a glowing red. Popular with the Greeks, Romans and the Victorians, pyrope is now in short supply. Tsavorite garnet comes in shades of green; rhodolite garnet ranges in colour from pink to reddish purple. Modern sources of garnet are the United States and South Africa.

Jade may be either jadeite or nephrite, both gem minerals that are correctly referred to as jade. The Mayans and Aztecs used jadeite for ornamentation and for medicine; Spanish explorers called the stone piedra de ijada -- "stone of the pain in the side" -- after seeing natives holding it to their sides to counteract aches. From ijada came the word "jade."

Jadeite comes in a wide range of colours, from greens and yellows to black and lavender, and is usually streaked or mottled. The finest quality jadeite is the vibrant emerald-green variety known as Imperial jade, named for the royal court of China that once cornered the market on this precious gem.

Nephrite's colours range from greens to yellow, brown, black, grey and white; the stone can be translucent or opaque, is usually mottled or streaked, and is very affordable and wearable. Nephrite's colours are generally more muted that jadeite's.

Because jade is exceptionally tough, it has long been prized by lapidary artists. It's one of very few gems that can be carved into rings and bracelets from a single stone, without supporting mountings or metalwork. In the Stone Age, Chinese workers fashioned nephrite into tools and weapons. Jade carving is still a national art form in China.

To improve its colour and appearance, jade is often treated by dyeing, waxing or bleaching. Jade sources include China, New Zealand, Russia, the United States, Canada and Taiwan.

Onyx is a variety of chalcedony, is characterised by straight, parallel bands which are usually black and white. This sturdy stone has long been popular with gem carvers for creating cameos as well as beads and cabochons. Modern sources of onyx are Brazil, Uruguay, the United States and Madagascar.

Opal is described as a "phenomenal" gem -- one whose colour defies simple description because of its many hues and special effects. Opals are divided into three main categories: white, which have white or light grey backgrounds; black, with black or dark backgrounds; and fire, which have red, orange, yellow or brown bodycolors and often don't show the "play-of-colour" typical of other opals. That flashing play-of-colour is a result of opal's internal structure: stacks of sub-microscopic spheres assemble in grid-like patterns, which cause light to bend and break into the colours of the spectrum. Opals may be treated by several methods, including oil or wax, to improve play-of-colour. Australia is a major source for black and white opal -- the gem is the country's national gemstone; Brazil (for white opal) and Mexico (for fire opal) are other producers.

Peridot is a stone prized for its cheerful green shades, was called "gem of the sun" by the Egyptians. Its plentiful supply and reasonable cost make Peridot a popular gem, and its beautiful colour makes it an exciting contrast when used with other vibrant stones like Citrine and pink tourmaline. Available in a range of colours from brownish or yellowish green to greenish yellow, Peridot is mined in Myanmar (formerly Burma), Pakistan and the United States. Period's name derives from the Arabic word faridat, meaning "gem."

Rose quartz is a budget-wise stone that ranges in colour from very light pink to medium-dark pink. Because rose quartz often has myriad internal fractures, the stone may have a translucent, cloudy quality or appear delicately veined, like jadeite. A durable stone, rose quartz is lovely when it's fashioned into bead bracelets and necklaces. Brazil and India are among the sources of rose quartz.

Ruby along with sapphire and emerald, one of the "Big Three" -- is a variety of corundum, the same species as sapphire. Its very name comes from the Latin word ruber, meaning "red." Available in a wide range of reds, rubies are especially prized in the vivid red "pigeon's blood" colour. Myanmar (formerly Burma) is considered to produce the finest rubies, but large, extremely fine rubies are rare and prohibitively costly. Fortunately for consumers, there are ample treatments and sources -- including Afghanistan, Kenya, Sri Lanka and Vietnam -- to make rubies affordable for most people. Many rubies are heat-treated or cavity-filled with epoxy resin or glass to improve colour and/or clarity; such treatments are detectable only to a trained gemmologist.

Sapphire along with ruby and emerald, one of the "Big Three" -- is a variety of corundum, the same species as ruby. In fact, if a corundum doesn't qualify as ruby, it's considered sapphire. Although most people think of sapphire as blue, it can actually come in colours from violets and greens to oranges and yellows to pinks and purples. These "fancy" sapphires include amethystine or plum (purple), golden, white or colourless, and the vivid padparadscha, which is pinkish orange to orange-pink. The latter term comes from padmaragaya, the Sinhalese term for "lotus colour" Heat-treatment to improve colour and/or clarity is common for blue sapphires. Sapphires can also be partly-coloured, displaying a combination of colours
The sapphire's place as a favourite gem of royals was reinforced in 1981, when Britain's Prince Charles presented Lady Diana with an exquisite blue sapphire engagement ring. Historically, India and Pakistan were the sources of fine blue sapphire; today, production is limited. A number of countries world-wide are the modern sources of sapphire, including Australia, China, several African countries and the United States.

Smoky Quartz is a durable stone that ranges in colour from light to dark brown, is an abundant and reasonably priced choice for a wide variety of jewellery. Smoky quartz may be heated to lighten its colour, or irradiated to deepen its colour. Once found in the Cairngorm Mountains in the Scottish Highlands, smoky quartz is a traditional gem there, where it's still known as Cairngorm. Modern sources for smoky quartz include Brazil, Switzerland and the United States.

Tanzanite is named after Tanzania, the east African country where the gem was discovered in 1962. Heat-treating the gem produces a range of colours, from light to dark shades of violet blue to pure blue. Tanzanite also possesses a quality called pleochroism, which means that it will show different colours when viewed from different directions; with tanzanite, the colour spectrum will be shades of purple and blue. To date, Tanzania is the only source of this gem.

Topaz comes in a wide range of colours, from colourless to blues, reds and purples, including the shades of brown that many consumers recognise. Topaz is usually named for its colour, such as blue topaz or pink topaz. Special trade names include imperial topaz, an expensive variety in shades of medium reddish orange to orange-red, and sherry topaz, with its yellowish brown or brownish yellow to orange shades. Consumers sometimes confuse Citrine or smoky quartz with topaz; the name itself probably comes from the old Greek name Topazios (now Zabargad), a Red Sea island which once produced Peridot, which was mistaken for topaz. Topaz varieties can come in very generous carat sizes -- the Smithsonian Institution houses the "American Golden," a light yellow topaz that's a whopping 22,982 carats! Common treatments for topaz are heat, which can change some yellow or brown gems to pink, and irradiation and heat, which produces most medium- to dark-blue topaz. Modern sources of topaz include Australia, Brazil, Mexico and the United States.

Tourmaline comes in such a wide range of colours that it's truly one of nature's most versatile gems. Before the development of modern mineralogy, at a time when gems were identified by colour, tourmaline was often mistaken for another gem such as emerald or ruby. The name tourmaline itself comes from the Sinhalese word toramalli, meaning "mixed gems." Tourmaline exists in a range of shades within its many colours Tourmaline varieties include rubellite, in pink to red shades; indicolite, in dark violet blues to blue and greenish blue; Paraíba tourmaline, named for the state of Paraíba, Brazil, in intense shades of violet-blue to greenish blue and blue; the intensely green chrome tourmaline; partly-coloured tourmaline, with its combination of colours, the most common of which is green and pink; and watermelon tourmaline, which displays a pink centre rimmed by green. Tourmaline's colour is often enhanced through heat or irradiation. Today's major source of tourmaline is Brazil.
 

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