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Garnet

Garnet

The name garnet comes from the Latin word granatus, meaning “seed,” because it often resembles small round seeds (similar to the red kernels of the pomegranate)when found. Garnets are isomorphous, meaning that they share the same crystal structure. This is a group of six differently colored minerals with similar crystal structures and related chemical compositions. The garnets can be divided into two series the pyrope-almandine series (“pyralspite” series) and the uvarovite-grossularite-andralite series (“ugrandite” series).

Red is the color which occurs most frequently, but there are also garnets showing different colors of green, pale to bright-yellow, fiery orange and fine earthy shades. Garnets are abundant in metamorphic rocks. Some of the best crystals are from schist, serpentines, metamorphosed limestones, gneisses, and granite pegmatites. They form under high temperatures and pressure. Garnets can be used by geologists as an indication of the temperatures and pressures at which the rock was formed.

There are six main garnet types used by the jewelry trade, they are pyrope, almandine, spessartine, grossular garnet, andradite, and uvarovite. The best known are the deep-red almandine garnet and pyrope garnets. Pyropes and rhodolites are usually free from flaws, whereas almandines are likely to contain flaws. Fine pyropes have been used as gems by royalty and the combined brilliance and fine purplish color of rhodolite have produced some exquisite transparent gemstones. In the 1960s, a new garnet was discovered which made green an important garnet color. It was named tsavorite, after the Tsavo area of southeast Kenya.

Garnet can be faceted, and those of deep color are fashioned as cabochons and are called carbuncles. Red garnets were the most commonly used gemstones in the ancient Roman world. Dark red garnet (carbuncles) was loved by Victorians.

Gem quality pyrope comes from Arizona and Utah; almandine from Alaska and Idaho; and rhodolite from North Carolina. It is also found in Australia, Ceylon, Czechoslovakia, South Africa, and South America.

Garnet is the first of the twelve gemstones of the ceremonial breastplate worn by the high priest Aaron, representing the twelve tribes of Israel as described in the Old Testament book of Exodus, and is also known as the month of the January’s birthstone.

Image from : https://gemfame.com

Content Source : https://www.energymuse.com/garnet-stone.html

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Flourite

Flourite

 Fluorite is also called fluorspar, from the Latin word fluere meaning “to flow.” It is a widely distributed mineral that is mined in great quantities. It occurs in mineral veins, alone or as a gangue mineral with metallic ores and in association with quartz, barite, calcite, celestine, dolomite, galena, cassiterite, spalerite, topaz and many other minerals.

Fluorite has many industrial uses: as a flux in the manufacture of steel; in the production of hydrofluoric acid; and as a catalyst in the manufacture of high-octane fuels. It is used in the manufacture of artificial cryolite, for the refining of aluminum, lead, and antimony, in the formation of opalescent glass and in iron and steel enamelware. Fluorite is also a source of fluorine, which is used for the fluoridation of water and in Teflon coating, where the fluorine helps to provide the “nonstick” surface on Teflon cooking pans.

Blue john is a variety of fluorite with curved bands of blue, purple, violet, yellow, and white. These distinctive colors were made millions of years ago either by the inclusion of manganese or oil. Blue john is fragile and may be bonded with resins to help protect against damage. The only source in the world for Blue john is Castleton, in Derbyshire, England. It was used by the ancient Romans for ornamental objects. It became very popular in the late 18th and 19th centuries, when it was used to fashion vases, urns, and dishes.

Fluorite is found worldwide. Major sources are found in the United States in Halliburton County; Hastings County; in Ontario, Canada; Trigo Mountains, La Paz County, Arizona; San Juan County, Colorado; Cave-in-Rock, Hardin County, Illinois; Franklin, New Jersey and Socorro County, New Mexico. Also in South Australia, and Alsace, northeast France.

Fluorite can be confused with many gemstones, due to its richness of color.

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Emerald

Emerald

Emerald’s name derives from the Greek word smaragdos, which in turn was derived from an earlier Persian word meaning green mineral. Emerald is a beryl, and is the best known variety of beryl.  Some of the world’s finest emeralds come from Colombia.

Emeralds were mined by the Aztecs and also by the Incas over 500 years ago; long before this, Roman and Greek civilizations used it.  It was mined in Egypt some 3,500 years ago. To the Egyptians it was a symbol of fertility and life. As early as 1300 BC, Emeralds have been mined in Upper Egypt. Most emeralds used in historical jewelry would have been from these mines and after the conquest of Egypt by Alexander the Great these mines became known as “Cleopatra’s mines.”

Emeralds have a cut specifically designed to minimize loss of material when cutting, this cut is called the “emerald cut”. Composites such as garnet, soude’ emerald, quartz, spinel, or glass are used to imitate emerald. Pale emeralds can also be painted or foiled on back to improve their color. Synthetic emeralds were first produced just before World War II and have been made in commercial quantities in the United States and elsewhere.

Emeralds were reputed to cure blindness; Nero was said to have had a monocle made of emerald.  It was believed to preserve the chastity of women, which, if violated, would cause the stone to burst into fragments.  Emeralds were also supposed to blind poisonous snakes.  It is a highly-prized stone for Muslims, as green is the sacred color of the Prophet.  In Asian countries it represents hopes of immortality, courage and exalted faith.

The oldest Egyptian mines were rediscovered by the French adventurer Cailliaud in 1816. Then in 1900, Cleopatra’s mines near the red sea were found.  Today emeralds can be found in countries and regions such as Russia, Pakistan, Norway, parts of Africa, Austria, Brazil, and the United States

Emerald is one of the twelve gemstones of the ceremonial breastplate worn by the high priest Aaron, representing the twelve tribes of Israel as described in the Old Testament book of Exodus, and is also known as the month of May’s birthstone meaning, love.

Source :

https://gemfame.com/product-category/emerald-stone-panna/

https://www.gemsociety.org

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Diamond

Diamond

The most precious of the four precious stones, including emeralds, rubies and sapphires; diamonds are the hardest substance in the universe. Its name derives from the Greek word adamas, meaning invincible. The diamond is the only precious stone that rates a number ten in Moh’s scale of hardness. Made of pure carbon the only thing that can cut a diamond is a diamond.  Its extreme hardness is the result of its atoms being compacted and bonded by high pressures and high temperatures in the Earth’s upper mantle. Because diamond is made up of carbon, it burns in oxygen or in air heated to a very high temperature.

 

Most diamonds came from alluvial deposits, (mainly river and beach gravels) until the discovery in the mid-19th century in South Africa, of pipe-like intrusions that had risen from great depths, and were filled with a variety of peridotite. Peridotite was later named kimberlite, because of it being first identified in Kimberley, South Africa. This igneous rock is rich in magnesium, iron, and calcium. These intrusions are also found in lamproitic rocks, which are the source of diamonds in Western Australia. Intrusions can remain deep in the Earth until volcanic eruptions force them to the surface.

 

In the past, diamonds were extracted by panning from weathered kimberlite in open pits, but as the pits became deeper and the rock harder, underground mining became necessary. Today, drill-holes are packed with explosives and blasted to break up the rock. It is brought to the surface and the diamonds are separated using grease tables.

 

Diamonds occur in two distinct varieties. Bort, which occurs as rough rounded masses with radial or confused structure, without distinct cleavage; it is grayish black with a specific gravity of 3.5. Carbonado, or black diamond, is opaque, granular to compact, and without cleavage; its specific gravity 3.1 to 3.3.

 

Crystals may be transparent, translucent, or opaque, and range from colorless to black, with brown and yellow being the most common colors. Colorless or pale blue gemstones are the most often used in jewelry. Red and green have long been considered the rarest colors, but pure orange and violet are much rarer and also more valuable.

 

Diamonds are measured in carats. The value of a carat has been standardized as 0.2 grams or 200 milligrams since 1907. The term “carat” is believed to derive from the weight of Mediterranean carob seed pods from the “locust pod” tree (Ceratonia siliqua), which have long been used to weigh precious stones. The name is derived from the Greek term keration, meaning “fruit of the carob.”

 

Diamonds have a perfect crystal form and high symmetry. Uncut crystals may look greasy and rounded, but when broken or cut, the faces show brilliant adamantine (diamond-like) luster and dispersion. These give the stone a fiery brilliance that is probably best displayed by brilliant cuts, which are the most popular today. Diamonds are generally insensitive to chemical reactions. High temperatures can produce etchings on the facets. Due to the optical effects, the high hardness, and its rarity, the diamond is considered the king of gemstones. It has been used for adornment since ancient times.

 

In ancient times, diamonds were thought to bring victory to the wearer, giving him superior strength, fortitude and courage. They were associated with thunder and lightning. It was also believed to indicate guilt or innocence, the stone growing dim if the accused was guilty and shining brightly if he was innocent. They were also believed to possess reproductive powers.

 

Since the late 19th century, South Africa has been the major source of gem-quality diamonds. Australia is a major producer of fancy colors. The Democratic Republic of Congo (formerly Zaire) once produced the largest quantity of diamonds, almost all being of industrial grade. Today more than twenty countries belong to the diamond suppliers circle. Important diamond producers include Botswana, Guinea, Russia, China, The United States, Brazil, Venezuela, Canada, and the Argyle and Merlin diamond mines in Australia.

 

The sale and distribution of diamonds is strictly controlled by the Diamond Trading Corporation to maintain a stable market. Diamond is known as the month of April’s birthstone meaning, innocence

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Coral

Coral

Coral polyps are marine plant-like animals and are extremely small, barely 2 millimeters in diameter. Coral’s external skeletons mass together to form tree like structures. They live in colonies, either in reef systems in warm, shallow water or in deep sea colonies. Coral polyps have a hollow cylindrical body, with a ring of tentacles around the mouth, and secrete an external chalky or horny skeleton. The coral grows as the polyps ingest small animals and plants, and secrete more of the skeleton-forming substances. Red, pink, white, and blue coral are made of calcium carbonate, while black and golden corals are formed of a horny substance called conchiolin. Coral has a dull luster when recovered, but can take a bright polish.

There are two thousand types of coral in existence. Coral is found at depths of 1-1020 ft (3-300 m), and mainly harvested with weighted, wide-meshed nets dredged across the seabed. When harvested by divers, not as many corals are damaged. Reef coral (including precious noble coral as well as blue, golden and black coral) and deep sea corals are the most threatened, primarily by the fishing industry, the rise in water temperature from global warming and deep sea oil and gas development.

There are different types of coral: sponge coral (often attached to reefs, it is not rare and inexpensive), it occurs naturally in reds, purples and yellows but is also dyed or stained; noble coral (also known as precious noble coral occurs both in deep sea colonies and in coral reefs with warm shallow water), it is very hard to polish which adds to its expensive price in the market. There are different types of noble coral: momo coral (beautiful light red to salmon color, often mottled with white areas); sardegna coral (very popular for its medium red color, if you see it in a bright red color it is dyed); angel skin coral (a pretty rose-pink color with whitish or light red spots – popular with jewelry makers); moro coral (has a darker, oxblood color – it is the rarest and most expensive type of noble coral and comes from the seas around Italy – very rare due to the damage caused to the reefs by overfishing and pollution); and Japanese red coral (red with white patches). There is also black coral (not a very important type – inexpensive – it is thought to be coral in an early state of decay); golden coral (like the black coral they consist of the hornlike substance conchiolin – found in the coastal waters of Hawaii and has a resinous or lacquered luster and texture); and blue coral (has very little value as a stone – blue coral is thought to be in the first stage of decay).

For the last 200 years, the main trade center for coral has been Torre del Greco, in the south of Naples, Italy. Three quarters of the coral harvested all over the world are still processed here. Deposits of coral are found along the coast of the western Mediterranean countries, the Red Sea, Bay of Biscay, Canary Islands, Malaysian Archipelago, the Midway Islands, Japan, and Hawaii in the United States. Production is increasingly controlled by environmental laws.

Coral can be confused with conch pearl, carnelian, rhodonite, and spessartite. Imitations are made from glass, horn, bone, rubber and plastics.

Information gathered from

https://en.wikipedia.org/wiki/Precious_coral

https://gemfame.com/gemstone-identification-chart/

 

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Citrine

Citrine

Citrine’s name derives from its lemon yellow color, and from the old French word citrine, meaning “lemon.” It is a yellow to brownish quartz (silicon dioxide) and resembles yellow topaz. Citrine has been popular for thousands of years and revered for its rarity. Citrine occurs in igneous and metamorphic rocks, particularly in granite and gneiss. It is also found in clastic sediments. Because it resists weather, citrine is also found in alluvial sands and gravels.

The coloring agent of citrine, is iron. The most valuable stones are the darkest, sometimes known as “Madeira citrine” for its resemblance to the color of fortified wine. Natural citrine is less common than amethyst or smoky quartz, both of which can be heat-treated to turn their color into that of citrine. Most citrine that is available in the market today is heat treated amethyst.

Citrine is found in localities that produce amethyst, and it is sometimes found as a zone of citrine in amethyst, when it is known as ametrine. Natural, bright yellow citrine is the rarest of the quartz varieties. Well-colored citrines are used as ring stones and pendants; less attractive stones are used in making necklaces or ornaments.

 The largest supplier of natural citrine is Rio Grande do Sol state in southern Brazil. Citrine mines in the United States are located in North Carolina, Colorado, and California.
Citrine is often confused with many yellow gemstones, especially apatite, golden beryl, orthoclase, topaz, and tourmaline, as well as tinted glass
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