Monday, July 28, 2014
PLACERVILLE, CALIFORNIA
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Rock doc: Chance discoveries in our backyards

By
August 20, 2010 |

Special to the Democrat

Some of us have never found a single dollar bill on the sidewalk. But once in a blue moon a lucky soul in the upper Midwest reaches down into the Ice Age deposits of our country and plucks out a diamond.

It doesnÕt take much geologic knowledge to recognize a diamond in the rough as an interesting and valuable object. Diamonds are the hardest mineral in the Earth, which means they will scratch quartz, window glass and even other hard gems like ruby and emerald. And diamonds have a very high luster, a term referring to their ability to reflect light.

In short, itÕs not too tough to identify diamonds, even before they have been shaped into cut gemstones.

ThatÕs why, since the 1800s, farmers and other residents of the Midwest have occasionally spotted and scooped up a diamond when digging water wells or otherwise disturbing the ground.

Most diamonds are found near the place where deep Earth processes blasted them to the surface in special rock material called kimberlite (named for Kimberley, South Africa). But there arenÕt rocks like that in the Midwest.

Instead, the diamonds in that part of the world were transported to their resting places by the enormous glaciers that dominated North America during the Ice Age. Geologists spent several generations looking for the ultimate source of the diamonds Òup iceÓ in Canada. ItÕs only recently that a few dedicated Ñ not to say obsessed Ñ geologists found the sources in northern Canada.

Geologists usually look for diamonds not by initially searching for diamonds themselves, but by looking for more common minerals that often come along with diamonds from their deepest sources in the Earth. Even so, finding diamond-rich rocks is generally a needle-in-a-haystack challenge. But, in time, dedicated exploration geologists found the source of diamonds in northern Canada that can Ñ occasionally Ñ be found in our upper Midwest. The fascinating tale of the search is one you can read about in the book ÒBarren LandsÓ by Kevin Krajick.

Other people discover objects of no monetary value but that mean a lot to those of us interested in Earth history. That was the case earlier this summer when a contractor in Tennessee digging 8 feet deep for a swimming pool unearthed a fossil. It appears to be the jawbone of a trilophodon, an extinct relative of the mastodon.

Mastodons and their kin roamed the Earth during the Ice Age Ñ the same time that a few diamonds were arriving to the Midwest courtesy of Canadian sources. YouÕll probably remember mastodons (dimly) from childhood books or posters about the Ice Age. Mastodons were browsers rather than grazers, a point scientists can deduce from the shape of their teeth. The woolly mammoths, in contrast, were the large and famous grazers of the era.

All the mastodon-related species went extinct as the Ice Age came to a close. That may be because enormous, natural climate change was sweeping the Earth. And it may be that many animals in North America were also facing increased pressures from human hunting.

No one is prepared to find Ice Age fossils when digging for a swimming pool. At first the folks in Tennessee thought they had found the jawbone of a dinosaur. Homeowner Jim Leyden got a call from his wife at home reporting exactly that. But a conservator from the local Pink Palace Family of Museums steered the understanding of the discovery toward the mammals of the Ice Age. (The Pink Palace features a wide variety of exhibits ranging from natural science discoveries to a replica of Òthe first self-service grocery store in the country, Clarence SaunderÕs Piggly Wiggly.Ó) The Pink Palace conservator estimated the fossil trilophodon weighed up to 2 tons.

The discovery in the pool pit was quite a surprise to all concerned.

According to a report from MemphisÕ Commercial Appeal, Leyden said, ÒI grew up in New Jersey. I might find a body, but not a prehistoric animal.Ó

Leyden told reporters he planned to donate the jawbone to the Pink Palace.

As he said to MemphisÕ WMC-TV, ÒWhat am I going to do with it? If I keep it around, my wife might throw it at me.Ó

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Follow her on the web at rockdoc.wsu.edu rockdoc.wsu.edu and on Twitter @RockDocWSU. This column is a service of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.

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