There are many types of sulfide minerals, but pyrite and marcasite, the two structural forms of FeS2 that are especially common in coal regions, are the major acid-producers.

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It treats the wastewater more effectively, and doesn't have any of the environmental drawbacks of that technology, such as production of unwanted hydrogen sulfide or possible release of methane, a potent greenhouse gas.

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In one Ikaria-funded study published in the Proceedings of the National Academy of Sciences, Albert Einstein College of Medicine's David Lefer found that low doses of hydrogen sulfide slashed heart damage by 72% in mice after heart attacks, even without inducing hibernation.

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When the Department of Environmental Protection noticed hydrogen sulfide in the city's water supply, Stephen Hollowell, general manager of Steinhatchee's chlorine-based water-treatment plant, and his board were willing to a take a chance on new technology.

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In 2005 he put mice into hibernationlike states with small doses of the toxic gas hydrogen sulfide.

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Hydrogen sulfide faces skepticism because of its mysterious nature and its potential for toxicity.

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When his staff gassed mice with hydrogen sulfide at a fraction of the lethal dose for humans, their body temperatures plunged, all movement stopped, and their breathing slowed to just a few breaths per minute.

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The capacity of mine containing cuprous sulfides and sulfides with disseminated PGMs is rising faster than mines deriving PGMs from nickel-rich sulfide ores, he said.

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