Any rock hounds here?

[Wade Lippman]

I found this rock on a beach in Maine. Part of it is like the granite like in most of the other rocks there; but what is the gray stuff, and why is it mixed in with the granite?rock.jpg

[John K Jordan]

Wade,

I sent your question and photo to a good friend of mine, a geologist. Don't know what she can tell from a photo but every time I've had an unusual rock in hand she had a reasonable explanation. I think sometimes chemical tests can provide definitive answers.

I found an unusual rock when leveling the ground near the house for a fire pit. She said no way that rock came from the ground in my area. Must have been moved here from elsewhere, perhaps in gravel fill when the house was built. Just looked like a pretty rock to me.

She's kind of entertaining on a road trip. Drive past a place with breakdown on a hillside from construction or erosion and she yells "Stop the car!" and gets out and explores.

JKJ

[Wade Lippman]

Thanks; maybe she will know.
Every rocky area I see I look for climbing routes. My wife examines every body of water for how good it would be for rowing.

[Lee Schierer]

It looks like a mix of pink and gray granite. Granite is pretty common in Maine.

[Jim Koepke]

It looks like a mix of pink and gray granite. Granite is pretty common in Maine.

Isn't New Hampshire the Granite State?

My wife is a rock hound and calls rocks like that leverite. As in leave 'er right there.

Her father used to call them 'sex stones.' An f-ing rock.

To me it looks like a piece of rough granite.

jtk

[Dave Anderson NH]

Many years ago I was out with a rock hound friend who had mined gems around the world. We were in northern NH which is almost all igneous rocks such as granite. We stopped at a place on the side of a back road he indicated and got out of the car. He showed me a feldspar mine long abandoned. Feldspar is one of the minerals in granite. Nearby were a couple of piles of a vastly different rock. After asking if I knew what they were. I didn't. He informed me they were Devonian Flint from the UK. He explained that when ships came to Portsmouth NH with trade goods they were ballasted with the flint which was then sent up to the mines via horse drawn wagon. The mines used the flint to grind up the felspar which was then bagged and wagoned to Portsmouth for shipment to England for use in making porcelain dishware. Hence flint 3000 miles from where it was found.

[Tom M King]

Maybe Gneiss.

[Bill Dufour]

Could be gray granite with inclusions of the pink. Or the other way around. v Depends on what was there first.
Bill D

[Wade Lippman]

The pink stuff is obviously granite. The gray stuff is completely uniform and doesn't seem like granite at all. There was a lot of pink granite on the beach (though most seemed to be finer grain) but none had the gray stuff in it.

[John K Jordan]

I found this rock on a beach in Maine. Part of it is like the granite like in most of the other rocks there; but what is the gray stuff, and why is it mixed in with the granite?rock.jpg

The geologist wrote:

"Well, the lay term "granite" covers a range of rock types. Although it's difficult to ID a rock from a photo, this looks like it has white quartz and gray plagioclase feldspar. Your friend may be thinking about pink granites with orthoclase feldspar. The orange color in this may be iron staining from groundwater, as the two kinds of feldspar don't occur naturally together.

If the orange is orthoclase, it may be a granite rock that was later intruded by a magma of a different chemistry. I'd have to see the rock to give a better answer.

The loose rocks in Maine could have come from anywhere north of there, as glaciers moved a lot of Canadian rocks south. So local bedrock isn't relevant. But I would have picked up that rock, too!

Regards, Susan "

JKJ

[Steve Rozmiarek]

I'm a bit of a rock hound, really enjoy the geology of my area. The geologist that John quoted is right. You can tell a few more things about it though, because of the tumbled rounded shape it traveled a long while in water, so you can be sure it originated some distance off. If it was originally uprooted by a glacier as would be likely in your area, then it then started moving in a stream and found it's way to where you picked it up. It also takes a long time for that much weathering, and that is a very old type of rock. If I found it here it would have come from a close little mountain range with some of the oldest rocks in the world.

We hunt for Fairburn agates here in water transported deposits from the ancient sea beds and reefs that used to exist here.