Some rocks from volcanoes break down to form black sand.

有些火山岩被撞碎后会形成黑色的沙。

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When these rocks break down into the grains that make up the sand on our beaches, their colour is mostly determined by the presence or absence of iron.

当岩石分解成为颗粒够成沙滩时，颜色则是由铁元素氧化物的存在与否决定的。

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But no damage is done if the fin strikes the sand sans-rider - there isn't enough weight to force a break.

因为长板在冲到沙滩上时板上没有重量和压力来造成鳍的损坏。

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More than 10 drillers have already received Department of Environmental Protection permission to use mine discharges for fracking, a technique in which millions of gallons of water, along with chemical additives and sand, are pumped down a well to break apart gas-bearing shale deposits.

WSJ: Pa. pushes drillers to frack with coal mine water