agate amethyst ametrine amorphous solid belgium bow drill brick calcination canterbury cathedral cape arkona carnelian ceramic chalcedony chalk chert chrysoprase citrine coesite cristobalite cryptocrystalline crystal structure diagenesis east anglia england english channel eolith europe ferrocerium fiorite fire flintlock flushwork framlingham castle frizzen fulgurite funnelbeaker culture gariannonum geyserite grimes graves hammerstone hypothesis iron jasper java applet jurassic jutland kent knapping lake superior agate lechatelierite limestone long melford mineral moganite moss agate mozarkite neolithic norfolk norwich cathedral obsidian onyx opal orbicular jasper oxygen percussion cap petrology poland pottery quartz quartzite rose quartz sard sedimentary rock shocked quartz silicification silicon dioxide smoky quartz somerset spiennes steel stishovite stone age surrey sussex thetford tinder tridymite vitreous quartzite wikimedia commons