bluestone •flagstone, ragstone •Blackstone, jackstone •sandstone • capstone • hearthstone •headstone • gemstone • whetstone •hailstone • gravestone •freestone, keystone •greenstone • Wheatstone •Tinseltown • ringtone • pitchstone •millstone • whinstone • siltstone •holystone • semitone •stepping stone • coping stone •baritone • acetone • dulcitone •tritone • drystone • milestone •limestone •grindstone, rhinestone •cobblestone • gallstone • brownstone •lodestone • soapstone • duotone •microtone • bluestone • tombstone •moonstone • touchstone •bloodstone, mudstone •sunstone • ironstone • undertone •monotone • cornerstone •Silverstone • overtone •kerbstone (US curbstone) •turnstone •birthstone • flavone • endzone •cortisone • ozone

bluestone, common name for the blue, crystalline heptahydrate of cupric sulfate called chalcanthite, a minor ore of copper. It also refers to a fine-grained, light to dark colored blue-gray sandstone. Deposits are extensively quarried as flagstone (paving stone) in New York and Pennsylvania and used commercially for buildings and paving stone.