Strange Rock Found While Prospecting in Maine

[placertogo]

I found this rock while prospecting in a small mountain stream this week in Maine. It is 20 inches long, 11 inches wide, and 3 1/2 inches thick and seems to be made of a hard metamorphic rock similar to the area bedrock. The pattern is what is usually called botryoidal and is on both sides of the rock. The pattern does not appear to be any kind of fossil. Quite interesting and I have never seen anything quite like it in many years of prospecting. What do you folks make of it?

[63bkpkr]

Howdy Placertogo,
I like the name! The rock is unusual. It reminds me of a mineral deposit that might occur at the bottom of a very deep river bed, usually that means a historic non running river. I've come across mineral deposits on rocks where the mineral has glued a gold nugget to the rock, have you ground up a sample of the rock and checked it for gold content? Other than the above it reminds me of plaster texture mud that someome sprayed on the ceiling of a room and let it build up. I hope someone else comes along with a response that sheds some light on your question, unlike mine.

63bkpkr

Hey, are there any caves in your area? It could actually be a mineral deposit from a cave system?? You might try to determine what mineral('s) the rock is made from.

[Produce Guy]

It kind of looks like a rock from a cave,like water splashing over it.

[placertogo]

There are no true caves in this part of the northeast. I thought of water action dropping onto a horizontal surface over a long period of time. The puzzling thing is that a similar pattern exists on opposite surfaces of this rock. For dropping water action to be responsible, one side would have had to be exposed to water over a long period of time and then the rock reversed and the opposite side exposed to the same action over another long period of time. Seems rather unlikely. The rock appears homogeneous and the pattern seems to have been carved out of the rock by water action perhaps aided by grinding action of particulate matter. I will take a sample and grind it today to see what come up. Just upstream from where I found this rock is a section of upended metamorphic bedrock of similar color. I have found a good deal of color between the cracks in that material.

[AU Seeker]

Placertogo,

Does this rock cleave as with slate, I mean if you you strike it on the edge does it break into sheets/layers?

If so it could be a type of Mudstone.

I see that it has a clean break on one side/edge, it could have broken off a point/end of a larger piece that had both sides of it exposed to the elements which could explain how it has the same texture on both sides.


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