Thursday, June 2, 2011

Agate Stone

Quartz is one of the most common minerals on earth, but the quartz family is actually made up of two separate branches. When most people think of quartz, they think of what is known as macrocrystalline quartz, which includes rock crystal, amethyst, citrine, smoky quartz and rose quartz. Macrocrystalline quartz, as the name suggests, has large crystals which can be distinguished by the naked eye. This type of quartz is mainly transparent to translucent, with a vitreous luster.

Banded Agate from India

The other type of quartz is known as cryptocrystalline quartz. It has microscopically (or submicroscopically) small crystals and is usually translucent to opaque, with a waxy to greasy or dull luster. This kind of quartz has fibrous and granular subcategories. The fibrous varieties are known under the name chalcedony, but this name covers a remarkable variety of stones.
Dendritic Agate from India

In practice, the name chalcedony refers to solid colored cryptocrystalline quartz, especially of a light color. The patterned varieties tend to have their own names. The most famous of these include agate, distinguished by its bands of colors; onyx, black and white layered (usually dyed to produce a uniform black); carnelian, a yellow-orange to reddish-orange, colored by iron; and chrysocolla, a rare vivid blue-green colored by copper.

The patterns of agate are so distinctive that a number of different varieties are commonly identified in the trade. They include eye agate, which forms ring shapes with a point in the center; dendritic agate, distinguished by its moss-like patterns; and fire agate, with an unusual iridescence.

Agate was used as a gemstone by the Egyptians at least 3,000 years ago. In modern times, agate has a special association with the Idar-Oberstein region in Germany. Idar-Oberstein was an important source of agate until the 19th century, and the region was favored with good local sandstone for producing cutting and polishing wheels, and water power to work the wheels.
Fire Agate from Mexico

Fortunately for Idar-Oberstein, large deposits of agate were discovered in Brazil in the 1830's, just as the agate mines in Germany were starting to be worked out. The agate polishing industry in Germany flourished as a result and produced high quality object d'arts, beads, rings, pendants, brooches and cameos.

Today agate continues to be mined in Brazil, but also in Uruguay, India, Australia, China, Madagascar, Mexico, Mongolia and Namibia.

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1 comment:

  1. India is the only country who introduced various gemstones including diamond to the world. There are many Hindu shastras written thousands of years before christ or for that matter any religion on this earth, about several gemstones, their religious importance, how useful to the mankind, how gemstones relates to impact of cosmic powers on human being etc. The present days description about gemstones are not so precise as was in ancient days in India. Lot of facts need to be brought to the light from our ancient hindu shastras for betterment of common man. Acharya, Hyd India


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