Obviously, agate is not from the mouth of a horse. It’s the combination of aphanitic quartz with specific circular patterns which is formed by regular changes of trace elements such as iron, manganese and nickel. As the complex form of aphanitic quartz, agate presents different shapes, such as Stalactite, Kidney and Tuberculosis.

In the ancient Chinese documents and materials, there is another fanciful explanation that agate is the product of ghost blood. In a book written by Wang Jia during the Jin Dynasty (265-420), he said that agate is the crystallization of ghost blood from the age of the Yellow Emperor (2697 BC to 2589 BC). According to the story, the Yellow Emperor eliminated Chi and other forces, as well as devils, filling valleys and streams with their bodies. The bones piled up as mountains. In ensuing years, blood crystallized into stones and the bones was turned into ash while the spinal cords became springs. Blood that turned to red stones became agates. Ironically, agate is the outcome of geological process. Underground lava that is ejected due to the activities of the Earth’s crust forms into stones when it cools off. The cooled hydrothermal lava that is rich in SiO2 solidifies into silica gel and then becomes hardened to fill the holes and gaps of rock. When this happens, it becomes agate. Usually, agate is translucent or transparent with its hardness of 6.5-7, specific gravity of 2.55-2.91 and refraction rate of 1.535-1.539.

The famous places of production include India, Brazil, America, Egypt, Australia and Mexico. In China, the provinces of Heilongjiang, Liaoning, Inner Mongolia and Hubei became famous places for agate production – with a major center in Fuxin in Liaoning province. Agates in Fuxin come in many kinds and colors, and they are considered ideal material for engraving. Exploiting agate in Fuxin dates back 8,000 years, and the city is famous for its Red Agate, Green Agate and Agate with Water. Since the beginning of the modern Republic of China, more agate ore fields have been discovered in Xunke city in Heilongjiang, Xinjiang, Tibet and Ningxia. An agate ore field that was more than six square kilometers was discovered in the northeast desert of Inner Mongolia in 1987. A large agate ore field also was discovered in the Shennongjia district of Hubei province.

As a result, the size and scope of old and new ore fields have reduced the value of agate while increasing supplies, which makes agate affordable even to average Chinese consumers. In ancient China, agate derivatives were so expensive that only rich buyers and officials could afford it. “The emperor of the Sui Dynasty (581-618) used to send ambassadors to the countries in the western regions and they received agate as national presents there,” Du You said in his book Tong Dian.

But while it’s less expensive today to buy agate, choosing which agate to buy is not easy work. Color, texture and transparency are the most significant to heed when purchasing agate. In gemology, the color of superb agate should be bright and pure, and the color layers should be thin. High-grade agate derivatives should have a smooth and high transparency, and the shape and pattern must be even and obvious, as well as having an exquisite and tough texture.

There are similarities shared by agate, Chalcedony and Jasper, but there are big differences in cost. Generally, agate has specific veins while chalcedony has no veins at all, and minerals in Jasper are usually mixed with clay or any other impurities. Jasper also has a dim luster and poor transparency.