History and General Information of Natural Agate Gemstones
The striped beauty of the agate is unparalleled in the world of gemstones. This Silica mineral which is also among the most common forms of chalcedony, comes in different shapes, sizes and colors. The agate is formed when the cavities in lava are filled with gas bubbles. As the lava solidifies, these gas bubbles fill up with water containing silica and alkali, finally coagulating into a gel. The distinctive bands are formed when the iron in the lava comes in contact with the alkali, leading to the formation of bands of iron hydroxide, as the gel solidifies and crystallizes.
Cross sections of agate often reveal stunningly beautiful band formations, and while most stones have tree-like rings, come exhibit a scallop pattern, eyes, and in rare cases even a landscape with trees. Agate is named after the Achates River in southwestern Sicily, where it was first discovered. It is one of the oldest gemstones known to man, and has been used by humans in various ways for the past 15,000 years.
Chemical Composition of Agate
Agate shares compositional similarities with quartz, and is chemically represented as SiO2.
Physical Properties of Agate
It is rated 5.5-6.5 on the Mohs scale for hardness, but in spite of this agate tends to crack and chip easily. It has a glassy look with a specific gravity of 2.60 and a conchoidal fracture. It belongs to the tetrahedral crystal system.
Color of Agate
The variety of colors in agate is astounding with some of the most common ones being blue agate, which has a light blue color, while the moss agate is dark green showing clear patches. The green and white variety is called tree agate, while the brown, white and red varieties are referred to as petrified wood. Being a porous stone, it is often dyed to enhance its color, and dyed stones are sold under the name Black Onyx.
Agate is most commonly shaped into beads or cabochons. In order for the beauty of the stone to be revealed, it must be trimmed and cut by an expert craftsman. The pattern of the stone is revealed when the rounded nodule, in which the agate forms, is cracked open, to reveal its intrinsic beauty.
Agates are usually translucent to opaque in nature. It needs to be polished well, so as to reveal its full charms. The stone looks extremely dull if the polish is not of a high caliber, as in its natural state, it is not a very pretty stone.
Price of Agate
The stone is found in plenty and is used to make jewelry, from necklaces to earrings to bracelets and rings. It can be bought for as little as $ 10, with the better quality stones increasing in price. Agates which has beautiful natural structures can command good prices.
Agate is found in many parts of the world, especially in Brazil, Germany, Italy, Mexico, USA, Egypt and India.
Many stones, which show any kind of patterning are passed off as agates, but in order to be called an agate, a stone has to show the band effect. Without it, the stone is just any other variety of chalcedony.
Interesting Trivia and Other Important Facts of Agate
Agates are of the oldest known gem stones and in ancient times was used a talisman and amulet. Bowls made of agate were popular among the Byzantine emperor. Mithridates, king of Pontus, was said to have more than 2000 agate bowls in his collection. European museums, especially the Louvre, have some of the finest examples of agate bowls, which was avidly collected by European royalty. It is widely used in making cameos and other ornamental objects. It is also used to fashion paper knives, ink stands, mortars and pestles, as it can easily crush chemicals, without harming itself.
Agates are said to make the wearer rich, likable and prudent, and those who wear this stone are generally able to persuade people. It is also supposed to be a stone which makes the wearer receive divine blessings, and also possesses the power of gaining victory over enemies.
Most agates have treelike rings, but when the bands show up as straight lines, when cut in the cross-section, the agate is called riband agate. An agate which shows different colored concentric circular bands is called a ring or eye agate.
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