Today the family took a jag down the road to tour an active gold mine that spans the area between the towns of Victor and Cripple Creek. The mountain was first mined in the late 1890s with underground mines, where miners brought out 1-3 oz. of gold per ton of rock. At one point in 1914, miners found an underground geode that was so rich in gold that they recovered 4000 oz per ton! This find is still known around the world as the famous Cresson vug. Now, the mine is a huge open pit operation that recovers 0.02 oz. of gold per ton of rock, but it's still enough to keep the mine going.
The deepest mine in the early 1900s went down 3500 feet, and the current surface mining operations are roughly only 1500 feet down. So, the pit walls are full of holes where the old mining shafts were uncovered, and every new blast has to be careful not to dangerously collapse the remaining tunnels underneath. I loved seeing this example of the new, bustling operations interfacing with 100-year-old history. Here are pictures of the quaint town of Victor along with high-level views of the mine pits.
The haul trucks were HUGE!!! They can haul 240 tons of ore and rock, and the mine processes 74,000 tons of rock every day during 24 hr. continuous operations. We got to take pictures next to a retired truck - look at the size of that thing! The tour guide explained the different kinds of rocks at the mine, one of which is fluorite (see pictured). The fluorite at this mine is a pretty purple color, and it indicates to miners that gold-containing sylvanite (metallic mineral with silver, gold, and tellurium) is close by! I got to take a few pieces of the fluorite home, since they have no monetary value.
Next on the tour was the processing operations. As a chemical engineer, this was the most fascinating part of the tour for me. The gold-containing ore is dumped into a crusher, then coated with lime to help with the next step of the process: leaching. The ore is spread in layers in a leach pit, where it is irrigated through with very low concentrations of sodium cyanide in water. The sodium cyanide leaches the gold and silver out of the rocks very slowly over time. After lots of other steps, the gold and silver is smelted together into a cone-shaped ingot and then sent to an external refinery for final purification. Definitely not the "panning for gold" method of the early days! That only gets you so far, then chemical engineering lends a hand. I got a picture with the crusher conveyor belt and the leach pit behind me.
Final stop of the day was the unbelievably cute Costello Street Coffee House! Their dark drip coffee was fantastic, and the dining room felt exactly like a place I would want to come back and enjoy a cup of tea with a scone. Wouldn't you agree?
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