有关玛瑙的简短英语介绍~

求有关玛瑙的简短英语介绍~谢谢

Agate is a common semiprecious silica mineral that has long been used as a gem and ornamental. Agate is the most common variety of chalcedony which is a form of quartz. Agate is, in fact, identical with quartz in composition and physical properties. Composed of silicon dioxide (SiO2), it has a hardness of 7, a glassy luster, a conchoidal fracture, and a specific gravity of 2.60.
Most agates occur in cavities of eruptive rocks or ancient lavas. These agates have a banded structure, successive layers being approximately parallel to the sides of the cavity. During crystallization, the colored bands are not disturbed. Varieties of agate are characterized by peculiarities in the shape and color of the bands, which are seen in sections cut at right angles to the layers.

Agate forms when gas bubbles trapped in solidifying lava become filled with alkali and silica-bearing waters, which coagulate into a gel. The alkali attacks the iron in the surrounding lava, and bands of the resulting iron hydroxide are created in the gel, which loses water and crystallizes, leaving the bands intact. Many agates, when cut in cross-section, reveal striking forms.
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Agate by Vivian Liu Agate Facts, Information and Description Agate is a variety of chalcedony which comprises cryptocrystalline quartz gemstones composed of layers of quartz, sometimes of different colors. Agate is usually found as rounded nodules or veins. The layers of quartz are often concentric. The composition of agate varies greatly, but silica is always predominant, usually with alumina and oxide of iron. Very often tiny quartz crystals form within the stone and add to the beauty and uniqueness of individual stones. These crystals are called drusy (sometimes misspelled as druzy). Many a time, lapidaries often cut just the drusy from an agate and jewelers use these drusy cabochons as the main stone or as an accent stone in their jewelry designs. Agate is the Mystical birthstone for September. It is also the birth stone for the Zodiac sign of Gemini. Agate is the accepted gemstone for the 12th and 14th wedding anniversaries. These colored gems find extensive use as talismans and amulets, future predictors, healing aids and are also used in many religious practices. Small samples of some or the other variety of agate is found all over the world. A hard stone, usually within the range of 7-9 on the Moh’s scale agates are found in all colors of the rainbow, although green and blue are quite rare. The colors and "scenes" in agate are endless. While agate is usually an inexpensive stone, some varieties or special stones with very unusual scenes or markings can be quite expensive. Well known varieties of agate are: moss agate, eye agate; and plume agate, which looks like it's filled with beautiful feather plumes. A variety of colors are seen in this wonderful ornamental gem. You will come across banded agate or moss agate which is a fascinating white or milky agate that looks as though it actually has black, brown, or green moss growing within. There is eye agate which has an eyeball effect. In recent years, Montana agate has gained wide acceptance in jewelry and well cut stones with nicely defined patterns often exceed the price of some of the better known semi precious stones. Plume agate is also expensive. Agate jewelry is high in fashion now for its natural colors and elegance. It's also highly collectible and grows in value over time. You can find brilliant selection of Agate jewelry in both traditional and contemporary styles to match every taste. We have it all with Agate Earrings, agate Bracelets, agate rings, Hair Jewelry, agate Necklaces. Agate is found all over the world including: the Africa, Asia, Brazil, Congo, Egypt, Germany, India, Italy, Mexico, Nepal, India and the USA. Folklore, Legend, Healing Properties: Agate is believed to discern truth, accept circumstances, and is a powerful emotional healer. According to legend Agate improves memory and concentration, increases stamina and encourages honesty. It helps people born under the sign of Gemini to remain calm and focused. It is believed to prevent insomnia and insure pleasant dreams, to enhance personal courage and protect one against danger. Agate provides a calming influence, increases concentration, perception, and helps to enhance one's analytical talents.