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QUARTZ, SPINEL AND CORAL

THE MINERAL QUARTZ

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 Quartz is one of the most well-known minerals on earth. It occurs in basically all mineral environments, and is the important constituent of many rocks. Quartz is also the most varied of all minerals, occurring in all different forms, habits, and colors. There are more variety names given to Quartz than any other mineral. Although the Feldspars as a group are more prevalent than Quartz, as an individual mineral Quartz is the most common mineral.

Most mineral reference guides list Chalcedony as an individual mineral, but in reality it is a variety of Quartz. It is the microcrystalline form of Quartz, forming only occurs in microscopic, compacted crystals. This page deals only with the crystalline forms of Quartz. Chalcedony is listed on its own dedicated page in this guide. Other important varieties of Quartz, such as AmethystCitrine, and Agate, also have dedicated pages due to their popularity and varieties.

Some forms of Quartz, especially the gemstone forms, have their color enhanced. Almost all forms of the yellow-brown variety Citrine are in fact heat treated. Much Amethyst is also heat treated to intensify color, and a green transparent form known as "Green Amethyst" or "Prasiolite" is formed by heat treating certain types of Amethyst. There is also a transparent sky blue form of Quartz crystals, as well as a wildly iridescent type that are synthetically colored by irradiation of gold. In some localities, Hematite forms a thin red or brown layer internally in the Quartz crystal, giving it a natural bright red to brown coloring, and sometimes even a mild natural iridescence.

Quartz frequently forms the inner lining of geodes. Most geodes have an inner layer of larger crystalline Quartz, and an outer layer of Chalcedony or banded Agate.

Quartz is an important mineral with numerous uses. Sand, which is composed of tiny Quartz pebbles, is the primary ingredient for the manufacture of glass. Transparent Rock Crystal has many electronic uses; it is used as oscillators in radios, watches, and pressure gauges, and in the study of optics. Quartz is also used as an abrasive for sandblasting, grinding glass, and cutting soft stones. It is also essential in the computer industry, as the important silicon semiconductors are made from Quartz.

In addition to all the practical uses, Quartz is essential to the gem trade. Many varieties are faceted as gems. Amethyst and Citrine are the most well-known gem varieties. Rose QuartzSmoky QuartzRock Crystal, and Aventurine are also cut or polished into gems. Small colorless Quartz crystals are worn by some as pendants for good luck.

Quartz is also a very popular among collectors. Certain collectors specialize their collection entirely on Quartz alone.

Excellent Quartz specimens come from numerous localities on all the corners of the globe. Only a few select localities are mentioned here. Some of the largest crystals, weighing many tons and yet still perfectly formed, come from several pegmatite mines in the state of Minas Gerais, Brazil. A very well-known French locality of excellent Rock Crystal clusters is Bourg d'Oisans in Isere, especially at the La Gardette Mine.

In the U.S., flawless Rock Crystal of exceptional quality and abundance comes from Arkansas, most notably in the Hot Springs area, Garland Co.; Mount Ida in the Ouachita Mountains, Montgomery Co.; and the Jeffrey Quarry, Pulaski Co. Very large crystals also come from the pegmatite mines in the San Diego Co., California. Lustrous, doubly terminated stubby crystals come from Middleville and Little Falls, Herkimer Co.; and St. Johnsville, Montgomery Co., New York, where they are known affectionately as Herkimer Diamonds. 

Although Rose Quartz is very common, good crystals are rare and only found in a handful of localities. These are mostly in Minas Gerais, Brazil, in Galileia (especially at Lavra da Pitorra); and in Itinga, in the Jequitinhonha Valley; and also at Newry, Oxford Co., Maine. 

Fine Smoky Quartz comes from the Pikes Peak area, El Paso Co., Colorado. The Alps contain two very classic occurrences in Switzerland in St. Gotthard, Uri, Switzerland; and in Chamonix-Mont Blanc, France. The finest Rutilated Quartz comes from Novo Horizonte and Ibitiara, Bahia, Brazil. Tall prismatic Quartz colored dark green from Hedenbergite inclusions come from Serifos Island, Greece. Exceptional Faden Quartz comes from the Dara Ismael Khan District, Waziristan, Pakistan.

SPINEL

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Spinel is a hard vitreous magnesium aluminum oxide that has been used as a gemstone for centuries. The beauty of spinel has caused it to be mistaken for ruby and sapphire in the past. However, spinel deserves to be recognized as a gemstone that is worthy of appreciation in its own right. Spinel occurs in a range of colours, such as rose pink to rich red; lavender to deep violet; light to deep blue, orange, yellow, brown and black.

The name spinel is thought to have come from either the Latin word, "spina", meaning thorn, due to its pointed crystal form, or the Greek word for "spark", in reference to its bright colour. Spinel has been mined for centuries and one of the most famous historical spinel gemstones is known as "the Black Prince's Ruby". As the name suggests, this is a red gemstone, which was thought to be a ruby. The "Black Prince's Ruby" was acquired by Edward, Prince of Wales in 1367. It is set into England's state crown and is held at the Tower of London.

Spinel is considered to be a soothing stone because of its calming energy. Therefore, it is recommended for those who are suffering from stress. It is also thought to encourage renewal and healing. Different healing properties are attributed to spinel depending on its colour. Red spinel is thought to enhance vitality. Both green and pink spinel are said to encourage love and compassion. Violet spinel is associated with spiritual development and yellow is linked to the intellect. Spinel is a non-traditional zodiac stone for Gemini and is associated with the planet Mercury. In feng shui, spinel is said to carry yang fire energy.

World-famous spinel gemstones include the Black Prince's Ruby, which is a 170 carat red spinel set into the English state crown and displayed in the Tower of London.

The Samarian Spinel is believed to be the largest fine spinel in the world. It is a red 500 carat gemstone that is part of the Iranian Crown Jewels.

THE GEMSTONE CORAL

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Unlike most other gemstones which are of mineral origin, Coral is organic, formed by living organisms. It forms from branching, antler-like structures created from coral polyps in tropical and subtropical ocean waters. When the coral polyps die, the hardened skeleton remains, and this material is what is used as a gemstone. Most coral is white, but nature can create coral in several other colors, including the popular orange to red forms. This Red Coral, or Precious Coral as it is often known by, is the most used gemstone form of Coral. In fact, the color known as coral is derived from the typical pinkish-orange color of many red Coral gemstones.

Coral is an ancient gemstone, and has been used for thousands of years. Aside from the lovely solid colors found in Coral, it can also have color zones or swirls, with white, pink, orange, and red being the most prevalent. Coral is naturally dull; polishing is required to bring out its glassy luster. Coral gemstones can be either solid or porous, depending on the polyp formation. Despite Coral's pretty colors, it is very soft and brittle, and does not make a durable gemstone. It is prone to both scratches and chipping. Due to environmental protection laws worldwide, production of Coral for the gemstone trade is on the decline.

Coral is used as cabochons and beads. It is also sculpted into small carvings such as flowers for pins and brooches. Small branches of Coral are sometimes stranded into spiky, dangling necklaces

Black Coral  -   Marine coral species of the antipatharia family with a black color.

Precious Coral  -  Also known as Red Coral, describes the marine coral species corallium rubrum (or several related species of marine coral). Precious coral has a natural pink to red color and is the most desirable jewelry form of Coral.

 Red Coral  -   Marine coral species corallium rubrum (or several related species) with a naturally colored light pink to deep red color.-  Most gemstone Coral is natural, but caution should be taken as some Coral, especially with a deep red color, may be dyed

Coral is found only in tropical to subtropical saltwater environments. Regions producing coral include the Red Sea, the Midway Islands, the Canary Islands, the Taiwan and Malaysian Coast, the coast of Australia, Italy, (Sardinia), and Hawaii.