Ball clay in Jilin province is one of the earliest recognized and discovered Neogene Period ball clay in China.

吉林球黏土是我国最早甄别和发现的第三纪球黏土。

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Baoren ball clay in Jilin is comprised of inordinate kaolinite , a small quantity of quartz and some other clay minerals;

吉林宝仁球粘土由无序高岭石及少量的石英和其它粘土类矿物组成；

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S. A. Resarches in recent years reveal that a lot of ball clay mineral resources occur in China and ball clay is exported from China.

近年来经过我们专题研究，甄别和发现了大量的球黏土矿区还有深加工产品，改进口为出口。

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A ball of clay is placed on a flat wheel device that turns quickly.

VOA: special.2009.09.09

People form containers by pressing a ball of clay into a given shape.

VOA: special.2009.09.09

But it's not just the bounce and speed of the ball off the clay surface that sets it apart from other courts, and makes the French Open an elusive tournament for some players.

CNN: Tennis interactive: Why clay is so different

On clay, the ball bounces much higher than on other surfaces, so players have to hit the ball at shoulder level.

BBC: Clay brings tension to surface

But on a high friction surface like clay, the ball will grip more and change the trajectory of the ball quite significantly.

BBC: SPORT | Tennis | Rules and Equipment | On the rebound