Carbo Ceramics ( CRR - news - people )(CRR, 73) , a Houston firm that makes various forms of "proppant, " particles (sand or a synthetic substitute) injected along with the fracking fluid to keep the fissures propped open after the pressure is withdrawn.

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Carbo Ceramics is a leader in making what's called ceramic proppant, which is the synthetic material, sand-based often, with chemicals that are injected into the fractured rock to hold open the cavities so the natural gas goes up into the piping that captures it.

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