Saturday, October 24, 2009

Maine Mineral Photo of the Day


This is a uraninite crystal from the Swamp #1 Quarry, Topsham, Maine collected in 1996. It is about the size of a pea with a chevron face and the high gloss surface typical of the Swamp #1 Quarry specimens.

The Swamp # 1 Quarry is a very small early 1900s feldspar mine which has produced some of the finest uraninite crystals in the world. I found this by waving a Geiger counter over the various pieces of quartz/feldspar dump rock until it squawked. Upon breaking up the chunk of feldspar with a sledge, this little bugger popped out. Uraninite is uranium oxide (UO2). In most of the Topsham granite pegmatite quarries the uraninite is at a higher oxidation level (UO6 or UO8) which causes the crystals to lose their sharp crystal faces and edges and become small, black, chalky blobs, ie. pitchblende, often mixed with a wide range of colorful alteration minerals such as autunite, torbernite, uranophane and others.

The uraninite locality at the Swamp #1 Quarry was discovered in 1958 by Clifford Trebilcock, Jr. of Topsham when he was 13 years old. The quarry was subsequently drained of water and his parents joined him in recovering a large number of high quality uraninite crystal groups. For many years Trebilcock stubbornly refused to say where in Topsham he was finding these uraninite crystals. Because the Topsham pegmatite district has hundreds of large and small quarry pits stretched out over a dozen square miles, competing collectors were stymied in locating where Trebilcock was making his finds. Only with the publication of Maine Mineralogy, Vol. 1 in 1994 did Trebilcock finally reveal that the Swamp #1 Quarry was his source.

Click here to embiggen.

Here's a nice photo of one of Trebilcock's early finds.

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