Conway granite Conway granite Conway granite is a typically pink mineral-rich igneous (or mesoperthitic) biotite granite. It is amphibole-free and of coarse particle size (with portions of the rock fine-grained or porphyritic). Conway granite has a relatively high concentration of thorium, at about 56 (±6) PPM; this amount is not enough to make the granite dangerously radioactive, but it is sufficient to make the rock a low-grade (almost certainly not economic, at least in the early years) source of thorium for a thorium fuel cycle. Geologist Edward Hitchcock named the granite in 1877 after the town of Conway, New Hampshire, which is
Harz granite crystals can be up to 18 mm across. Birkenkopf granite was quarried on the Großer Birkenkopf hill south of Hasselfelde. It is a medium-grained granite with blue-grey coloration. In the quarry 30 to 40% blocks of stone could be used for sawing and 50% of exploitable rock debris could be obtained. The quarry closed in 2009. Birkenkopf granite contains 31.3% quartz, 42.6% alkali feldspar, 20.4% plagioclase feldspar, 5.4% biotite and chlorite as well as 0.3% ore minerals like magnetite, pyrite and hematite. The quarry for Wurmberg granite was situated about 2.5 kilometres north of Braunlage and 250 metres high on