found and smelted. Remains of Bronze Age copper mines can be found, for instance, in various parts of...process, the resulting deposit is a cassiterite greisen. Other examples of hydrothermal products are agate...can also concentrate on one or a few particular mines but only if these are being worked at the time and...hand lens with 10 X magnification. Quarries and mines are the best places to visit, but it is usually...cavities of certain basaltic lavas. USA - copper mines of Keeweenaw Peninsula, Michigan, crystals ( !