Regarding Joe Poor’s pro-mining letter: The difference between glaciers and mining companies is intention. Glaciers have none; they simply obey gravity and grind up whatever rock they encounter. Miners obey investors and grind up ore bodies likely to contain valuable minerals. Unfortunately, these are often, as with Constantine’s claims, high sulfide deposits. The tailings, unlike glacial till, generate sulfuric acid which leaches toxic heavy metals into water bodies. Copper, for example, is toxic to aquatic…