Wednesday, September 29, 2010

Adirondack Geology: Some Fascinating Rocks

I was going to write about skunk cabbage today, but I find myself sitting in a local rock shop where the proprietors offered to let me use of their Wi-Fi. Surrounded by all these geological wonders of the world, I feel compelled to tip my hat to some of our local geologic treasures.

As I’ve mentioned in the past, geology isn’t my strong suite, but I sure do love rocks. I suspect most of us do. Who hasn’t, at least as a kid, stuffed his or her pockets with rocks found along beaches, roadsides, or in gardens? Some of us never outgrow this obsession. And even though geologic terms run through my mind like sand through an hourglass, I am drawn to the varied forms and colors that most of us only encounter in rock or New Age shops.

When it comes to local (Adirondack) rocks of note, the one that springs first to mind is garnet. Garnet is found in pretty good quantity in the North River area, where Barton Mines is the primary business capitalizing on this semiprecious gemstone. I have been to programs where Barton representatives gave presentations, and it is simply amazing what garnet is used for. Most of us probably think of garnet as a lovely wine-red stone that is featured in jewelry and is January’s birthstone. But at Barton, much of the garnet that is mined is used for things like sandpaper, or to make a blasting compound that is used to etch glass. Who’d have thought it?

A mineral that we find in pretty good quantity around the Park is mica. Usually we only find little bits of broken flakes, but I have found small sheets sitting on top of the ground. In North Creek, at the Ski Bowl Park, some folks put in a lovely garden, complete with some terrific boulders. On these boulders are fanned protrusions of mica, thin sheets, stacked one on top of another, and then fanned out and emerging from the hardened grasp of the rock – it is amazing to behold.

Labradorite is a feldspar mineral found in large crystal masses of anorthosite. For those who don’t know, anorthosite is one of the major rock types in the Adirondacks, or at least in the High Peaks. It is a very old rock, not common on earth and found on the moon. One of the neat things about labradorite is the way it can shimmer with colors, an effect called labradoresence, or the schiller effect. Lesley, one of the shop owners here, showed me some labradorite rocks she picked up from the Opalescent up near Calamity Brook in the southern High Peaks. She polished them up and there, when the light catches it just right, it looks like blue and green northern lights skittering across the glossy surface. Of course, I had to purchase one for my collection.

Another interesting rock here in the shop is moonstone, which is a type of feldspar. Apparently rockhounds used to be able to mine it up in Saranac Lake. It isn’t a rock with commercial value, except in the rock-collector’s world. Lesley showed me a large chunk she got from up in Saranac Lake, as well as some jewelry made from small polished bits of moonstone. Like the labradorite, it has a bit of the schiller effect – a blue, green or even pinkish dash of color when the light hits it just right.

For those interested in Adirondack geology beyond the academic level, rock shops are the place to go. The folks who run these places love rocks and geology and are always willing to share their passion with others. I wrote before about the shop at Natural Stone Bridge and Caves, but other rock shops dot the park, like Lesley’s Minerals Unlimited in Long Lake. While much of her merchandise is from other parts of the world, she has a nice collection of local rocks and minerals that make a stop here well worth the drive.

Photo credit: Labradorite, courtesy Wikipedia.

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Ellen Rathbone

Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.





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