Go to the antique market and buy a bracelet with agate beads, only to buy a glass, or even plastic?
How is agate formed, and where can we possibly pick it up?
How is agate formed?
Agate is made up of silica and belongs to the large family of quartz, which is a very common mineral on the earth's surface.
However, unlike transparent and shiny quartz crystals, agate has a more warm and jade-like feeling, because agate is composed of many tiny quartz crystals, which are so small that they cannot be directly seen by the naked eye, and they need to be seen with the help of a microscope.
This type of quartz is called "cryptocrystalline quartz", and they come together to form unpatterned chalcedony and patterned agate. Because the particles are small, the agate converges the sparkle of the crystals and becomes more warm and subtle, so the ancients also called it "Qiongyu" and "Red Jade".
Chalcedony without patterns
To form an agate, you first need a cavity, for example, there are many holes in the volcanic rock. Oxygen- and silicon-rich hydrothermal fluids then flow through the cave and slowly crystallize from the cave walls to tiny quartz crystals, known as agate, layer by layer under certain temperature and pressure. If the crystallization speed is slower, larger quartz crystals can also be crystallized, forming geodes.
geode
Elements such as manganese, calcium, and magnesium in the hydrothermal fluid, affected by the temperature and pressure in the surrounding environment, crystallize in different sequences, so that the agate has a rich pattern color and presents an obvious concentric ring structure.
Concentric ring-like structure of agate
The pattern in the center conjures up a "vulture"
图源：wikipedia
Onyx inventory
There are different types of agate produced in many places in South Asia, the Middle East, and the Americas, such as "lace agate" in Mexico and "scenic agate" in the United States. Agate species in China are more abundant, from Heilongjiang, Liaoning, Hebei, to Inner Mongolia, Ningxia, Xinjiang, as well as Jiangsu, Sichuan, Yunnan and other places, there are agate production.
Scenic Agate: See the world in a stone
图源:amusingplanet
There are many "raisin" agate on the Gobi Desert in Xinjiang, Ningxia and Inner Mongolia, which are originally formed agate, which have been stripped out of the rock layer after the baptism of wind and sand, and can be left on the Gobi Desert for a long time because of the stable nature of silica, just like a bunch of raisins.
"Raisin" agate, don't bite into it
Source: etsy
Liaoning Fuxin agate has a long history, as early as 7,000 years ago Chahai people have used agate to make tools, Liao Dynasty here agate mining, processing technology reached a very high level. Aquatic plants and agate are produced in the southern part of Tibet, and there are aquatic plants-like patterns formed by mineral accumulation.
It looks like a mossy agate
The rain flower stone in Nanjing, Jiangsu Province is also the product of agate being eroded and rounded by flowing water, showing beautiful textures.
Nanjing Yuhua Stone
In addition, there are fire agate with halo effect, glittering agate with black bands of light moving when turning agate, agate agate with red goethite inclusions, freshwater agate that can produce fluorescence, and agate with star effect.
Fire agate with halo effect
图源：Maricopa Mining LLC / wikipedia
Silk agate with fine lines like ribbons, brocade rhino agate with rich colors, zygotic agate with white lines around the black body, brocade agate with red and white stripes, mushroom agate with stripes like mushrooms, and many other species.
Such as a silk agate wrapped in a ribbon
Special agate
1
Water urchin agate
● The inside of the agate is wrapped in liquids and gases, and the sound of water can be heard when it shakes, and the cavities left by the inward growth of the agate give these liquids and gases space to exist.
● The carver skillfully carved the water urchin into bubbles spit out by fish and shrimp, and Li Bai's drunken wine tank, etc., making the work more vivid. Iron can also turn water urchin agate into the rarer blood gallbladder agate.
2
Sengoku red agate
● It is a new agate variety on the market in recent years, mainly produced in Chaoyang, Liaoning and Xuanhua, Hebei, mainly red and yellow, and named after the same material as some jewelry in the Warring States Period. Red and yellow have been the colors of the Chinese since ancient times, so they are very popular.
3
Southern red agate
● Many of the "red jade" in ancient books refer to southern red agate, which is produced in Yunnan, Sichuan, Gansu and other places. The ancient Dian period has been mined and utilized, Xu Xiake once recorded the high-grade agate of Yunnan Agate Mountain, referring to the southern red agate of Yunnan Baoshan. After a large amount of mining in the Qing Dynasty, the output was reduced, and in recent years, the output has gradually increased after the improvement of mining and processing technology.
In recent years, the southern red agate produced in Diebe County, Gannan, Gansu Province and Meigu County, Liangshan, Sichuan Province has made up for the lack of production of Baoshan agate, and in order to distinguish it from the old mines in Baoshan, Yunnan, the southern red agate in these two places is called the new mine.
There are also some natural agate shapes and textures that are more peculiar like animals and plants. Discovered in Bayannur City, Inner Mongolia, the "Chick Out of the Shell" is such a masterpiece of nature, from the shape of the eggshell to the demeanor of the chick, it is vivid and lifelike.
Image source network
How to distinguish real and fake agate?
Like other gemstones, the agate market is also mixed, with many imitation agate products made of plastic and glass, which are very similar to the colors and patterns of natural agate, making it difficult to distinguish. Generally, it can be identified from the perspectives of texture, touch, density, gloss, transparency and hardness.
texture
The peculiar formation process of agate means that it should have a concentric ring-like structure. However, many agate jewelry only uses a part of the whole agate, cut and polished, and the texture is not complete, which is difficult to identify.
Haptics and density
Natural agate is cooler to the touch, denser and heavier to weigh, which can be distinguished from mild, lightweight plastic imitation agate.
Gloss and transparency
Natural agate has a waxy luster, is translucent, and often contains impurities inside. However, many imitation agate made of glass material has a vitreous luster, high transparency, and is easy to contain bubbles, which can be distinguished from natural agate. However, it is now also possible to imitate the wax texture by sticking an organic film to the surface, or to add impurities to the glass to reduce the transparency.
hardness
The hardness of quartz is 7 on the Mohs scale, so the agate composed of quartz particles is harder and belongs to the harder gemstones, and cannot be scratched by stones with a hardness of 7 or below on the Mohs scale, while imitation agate made of other materials such as plastic can be scratched.
In addition, there are some that pass off low-quality agate as high-quality agate. Usually from the super, first, second to third, the weight is from >5kg, 5-2kg, 2-0.5kg to <0.5kg, high-quality agate has the characteristics of pure color, beautiful pattern, no crack impurities and so on.
Agate turtle
Low-quality agate often needs to be injected and dyed to improve the quality, resulting in a color that is not as naturally bright as natural agate, and affected by the dyeing process, it is often darker where there are cracks, and lighter in the places away from the surface and cracks.
In short, in the actual situation, it is necessary to comprehensively use various methods to identify the authenticity and quality of agate.