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Agate is a striped chalcedony quartz that forms in layers and in a wide variety of colors and textures. An individual agate forms by filling a cavity in a "host" rock. As a result, agate often is found as a round nodule, with concentric bands. In ancient times it was said to quench thirst and guard against fever, and agate bowls were very popular in historical Europe. Amazonite is an aqua green and white feldspar. Named for the Amazon River, it is actually mined mostly in Russia and Colorado. The name "jade" is commonly used for two different silicate minerals, jadeite and nephrite. Prized for its color and hardness, jade has been used since ancient times for practical and decorative purposes. In China, it was once considered more valuable than gold and silver and was used for axe heads and other weapons. Ancient natives of Central America, New Zealand, and Egypt also prized jade as a beautiful and symbolic gemstone. Rutile is a crystal form of titanium oxide and ranges from nearly black to golden in color. Transparent quartz showing sprays of thin rutile crystals within has been used in jewelry and ornamentation since ancient times. Rutilated quartz often contains sprays of golden rutile so fine they look like hair and thus the stone is also known as Venus' hairstone. A lapis-rutile doublet has transparent rutilated quartz on top with a blue lapis backing.
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