A Qing Dynasty agate snuff bottle

For Chinese people, agate symbolizes longevity and is said to elevate the mood, giving people confidence. In traditional Chinese medicine it was used to treat eye ailments by placing it on the eye area. Rubbing it on the skin is said to soften the skin.

"Agate tastes spicy. It is a yin (cold energy) stone," according to "Ben Cao Gang Mu" ("Compendium of Materia Medica"), an ancient text on traditional Chinese medicine. Rubbing it on the body would help reduce excess internal yang or heat.

The "seven treasures" of ancient China by some accounts include agate, gold, silver, colored glaze, white coral and red coral.

People like agate for its many colors, its stripes or rings. Agate is a micro-crystalline quartz, chiefly chalcedony, with fine grain and bright colors. It is associated with volcanic rock and some metamorphic rocks.

Red agate is also known as chuyu, red jade.

"Although agates can be various colors, the most precious agate is red," says Lu Maofeng who owns an antique shop on Yongjia Road in Shanghai and has collected agate for many years.

The most precious agates are red with yellow inside, known as fire agates which can also be green, purple, and milky in color.

In addition to being kept as lucky stones, agates were carved into bowls, cups, snuffboxes and others items.

"Many treasures are made of agates and other precious materials like gold and jade," say Lu.

One of the most well-known antique agate items is the "Golden Ox Head Agate Cup" from the Tang Dynasty (618-907 AD), displayed in the Xi'an museum of Shaanxi Province. The cup is 6.5 centimeters by 15.6 centimeters. The horned ox head is delicately carved. There's also a mouse of gold inlay.

There are many agates on the market and it can be difficult to find a really fine stone. Master Lu gives some tips:

Agates naturally come in red, white and amber. The blues, purples and other unusual colors are probably artificially colored and will fade in a few years.

Look for bright, vivid color and clear visible red strips are composed of tiny red spots, visible under magnification.

Fake agates are, too, colorful but not naturally bright. They are not as hard as true agates. You can scratch a fake agate with a piece of jade; a true agate can't be scratched.

Real agates are translucent, sometimes murky, the grain can be seen. Fake agates are clearer, often transparent.

Real agates are denser and heavier than fakes.

Real agates will be hot in winter and cool in summer, while fake ones reflect the temperature, cool in cold weather, warm in hot weather.

(Shanghai Daily December 30, 2008)