They can be several hundreds of metres long and extend to depths in excess of 1,500 metres. Mineralization commonly occurs in shoots within the vein structures. Many outcrops of good looking veins are barren of gold or other ore minerals, but rich ore shoots may occur unexposed on surface, either down dip or along strike. Therefore, geochemical pathfinders are required. Many more recently developed deposits have larger tonnages and lower grades and can be mined economically thanks to more efficient mining and milling methods.
Mining requires adits, drifts, shafts and narrow slopes.
If a vein system occurs near the surface it may be possible to mine by open pit methods which would greatly reduce mining costs. The three types grade into one another. Gangue mineralogy includes quartz, amethyst, chalcedony, adularia, calcite, rhodochrosite, barite, fluorite and hematite. They have a relatively short but productive mine life, providing a quick payback and high rates of return on modest amounts of invested capital. Alteration of Vein Minerals Sulphide minerals oxidize readily to sulphates, many of which are soluble in water.