Natural stone contains silica too, so it's not clear that these workers would be silicosis-free if they'd been cutting e.g. granite instead. Average granite is

Natural stone contains silica too, so it's not clear that these workers would be silicosis-free if they'd been cutting e.g. granite instead. Average granite is 72% quartz: https://en.wikipedia.org/wiki/Granite#Chemical_composition https://en.wikipedia.org/wiki/Granite#Chemical_composition