Firstly, it is Hydraulically mined; that is, in the latter part of the 19th century earth was removed with high pressure water to devices that removed gold by washing the soil. Secondly, the silica AMT is after is in the form of common sand composed of SiO2 and/or larger pieces of rock high in silica, probably from a sedimentary rock called quartzite. Silica is most commonly used in the manufacture of glass which is nearly 100% silica. MSHA, the Mine Safety and Health Administration, routinely checks for silica in the air to make sure dust suppression procedures are being followed. Your community will be in no danger and with proper reclamation procedures(which were not done in the 19th century) your community should reap the benefits of high-paying jobs.