Sunday, April 18, 2010

Panning for Anatase in Harford County: Part II

Ev parked along the country road paralleling Falling Branch opposite from where a small rivulet flowed into it from the adjacent wooded hillside. We removed from his trunk our waders, rubber gloves with cotton gloves to wear under them, two shovels two buckets, one with 1/4 holes drilled into the bottom third, pans, Ev's "sucker," and baggies. Casing out the stream, Ev pointed out and expressed his preference for spots where the velocity of the water changed, better in front of rocks around which the current swirled with at least some downward motion. He was also eager to pan at the mouth of the small rivulet

As I watched from the bank, Ev waded into the stream, secured his buckets, one placed into another for drainage from top to bottom, and began digging beneath the downstream side of a rock the current was circumventing. For each load, Ev extended his shovel all the way down to scrape the bedrock where gold, as the heaviest substance in the stream, tends to gravitate. Anatase, though nowhere near so heavy as gold, has sufficient specific gravity to do likewise.

After tossing away the larger rocks, Ev turned the linked buckets sideways at an angle to the current to sieve the sand and smaller pebbles to the bottom bucket through the holes in the top one. After repeating the process several times, he transferred the contents of the bottom bucket into the pan.

Since some of the additional sand remaning in the stream beneath the rock ledges was likely to be relatively heavy, Ev scraped the area, seeking out small pockets with a screwdriver before going to work with the "sucker" he is holding in the image at right. He covered the smaller tube with the larger one and placed the tip under the ledge. While holding the smaller tube in place, he pulled on the larger one to suck out water in which additional sand was dispersed. This he poured into the pan.

The next step was the actual panning to reduce the pan's contents to heavy "black sand," much of which would prove to be magnetite. To accomplish this, he held the pan in the stream and swirled its contents back and forth. With assistance from a reasonably mild current, the lighter sediment washed away while small pebbles he removed by hand trended toward the top. A layer of lighter sand settled beneath them. The heavier black sand, meanwhile, gravitated to the bottom of the pan or became caught in the cavities built into its side. This work takes a few minutes and can be tedious. Upon completion, Ev placed the remaining black sand into a marked baggie.

Ev then repeated the entire process where the rivulet entered Falling branch. When finished, he suggested I grab a shovel and try my luck in front of another rock surrounded by swirling current. Albeit with much less finesse, I followed all the previously described steps and eventually produced a small quantity of black sand. We placed it in a marked baggie and headed back to Ev's house, put the sand in his oven to dry, and drove into Jarrettsville for lunch.

When we returned in about 45 minutes, the sand had dried. After removing with a magnet the predominant magnetite, we placed what remained into three film canisters. The fruits of our morning's labors were now ready for observation under Ev's microscope. Checking a few small samples, we found fragments as well as crystals of garnet, minute cubes of goethite after pyrite, specks of pyrite, possibly some beryl, a few black octahedra (Were they chromite? Why didn't I think to retrieve that magnet?), and occasional rough grains of anatase. Ed removed the most interesting material with a special pair of microscopically tipped tweezers. After two hours, we had examined but a small fraction of the sand.

A week has now passed, and Ev just emailed me that he has finished going through the sand from the first two of our three digs. While his second dig at the mouth of the small rivulet hadn't yielded much, his first dig of the day ended up producing "210 little pieces of blue, bark blue, tan (the most), and yellow (the least) anatase," including 3 dark blue double pyramids (all broken),and two sky blue very small flat topped pyramids (complete), and 2 dark blue flat plates.

Meanwhile, I've been out of town over this past week and before leaving had time to check out but a small sprinkling from the film canister bearing the fruits of my own first attempt at panning. A portion of of it is shown at left. Eyes still relatively untrained for spotting anatase, my inclination had been to delay going through the rest until the list of activities on my busy to-do list slowed down a bit. After receiving Ev's recent email, however, a few of the them could have to wait.

1 comment:

  1. Could you describe or perhaps picture the forceps he uses to manipulate the Anatase crystals and fragments?