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Freshly-fractured crystalline silica, such as that emitted during mining and processing, is significantly more toxic than "weathered" silica (from, e.g., agricultural sources,, apparently through reactive oxygen species generated mechanically (  This same source suggests a half-life of freshly-fractured silica of about 30 hours.

There is also evidence that freshly-fractured silica causes more lung reactivity and inflammation than weather ("aged") silica:,