- Associated Press - Saturday, May 3, 2014

HOLDING TOWNSHIP, Minn. (AP) - Ed Opatz spotted the agate first.

Look for it, he encouraged. It’s got purple bands. Red bands. A perfect example. Four of us stood in a tight circle, but only Opatz saw the agate. He released it from the dried grass binding it to the moss-covered, rock-strewn ground. Admired it. Eventually dropped the thumb-sized stone into the worn camera bag with the rest of the day’s finds.

We’d been exploring the concave cut of a small, privately owned gravel pit overgrown with weeds dried beige and rattling in the wind. As we headed back to the vehicles with ankles full of prickers and a couple of finds, we were wondering how many generations of kids had combed the site.

Opatz was still looking.

Opatz, 55, who runs an excavating business out of Holdingford, is always looking. On days like this one, he’ll spend a few spare hours walking a farm field, inspecting a dirt pile, checking out the long-abandoned, shallow pit. Sometimes he’ll arrive at a job site an hour early to hunt agates.

He started seeking the rust-and-white bands of Lake Superior agates - and their many variations - long before rocks from several states took over his garage stall. Long before his wife started measuring his collection in tons, not pounds. Long before he became president of the Cuyuna Rock, Gem & Mineral Society.

Opatz first noticed agates when he worked alongside his father, who ran a road construction business. When he was about 10, he recalls taking an ice cream pail and a day off to search for agates.

While thousands scour the Lake Superior shore for the banded rocks, Opatz said far less known farm fields and gravel pits hold more promise.

“Most people don’t realize it, I think. Most say, ‘I didn’t really want to go to Lake Superior.’ I wouldn’t. There’s been 10,000 people there. Unless you’re going after deer hunting and there’s been some 4-foot wave action,” Opatz told the St. Cloud Times (http://on.sctimes.com/RXAvQB).

The best agate-hunting spots in Minnesota are apparent on a map- a map of the path glaciers took some 10,000-20,000 years ago.

“It’s really hard to say when the agates got dropped into Central Minnesota,” said Robert Wichman, a St. Cloud geologist and professor. His focus tends to be on harder rocks, especially because four or five major glacial events occurred before the last ice age.

Lake Superior agates formed about 1 billion years ago - give or take 100 million years - when volcanoes spewed as the continent started to split in half. Gas bubbles trapped within the lava became the agates’ mold. According to a Minnesota Department of Natural Resources explanation, each band in a Lake Superior agate was formed by another layer of iron-rich dissolved minerals coating the pockets.

Agates popped free as the glaciers froze, thawed and ground southward.

“The agates got carried along for the ride,” Wichman said. “That’s why we find them.”

Glacial lobes that followed the Superior Lobe rearranged some, buried others. Wichman said an intact Lake Superior agate reveals the size of the hole in which it formed. Most agates are pea-sized, according to the DNR. The largest ever found were the size of bowling balls.

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