What is this rock?

[sjb]

I am stumped with this rock. I have never had a rock cause such an overload on my metal detector. I have a new Minelabe Safari and took it to the beach. It signaled gold and of course we dug, dug dug. About two feet down, there were rocks, and we took them out of the hole one by one. This rock was the cause of the beeping- and every time we test it, it causes the machine to "overload" with such a strong signal. The dark grey color of the rock rubs off on our hands, and we can write with it (like it is graphite or something). There is a vein of quarts and shiny material that runs through the rock. Any thoughts?

http://s994.photobucket.com/albums/af66/sjbgarden/Rock/

Thanks!

 

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[Tuberale]

Appears to be gneiss to me. And therefore needs to be addressed more carefully. Gneiss often is associated with quartz and gold. Indeed the closeups seem to show small golden nuggets in them. But may just be the appearance of gold. Gneiss is often associated with other metals as well, and I don't see how the outer covering would come off in your hand if it were gneiss.

Here's a thought, though: break the rock with a sledge hammer or splitting maul. Post a photo of the interior. If there is much more golden colored material inside ... it may be time to consult a geologist.

Another thing that would help the rest of us: where did you find this? Don't have to be specific, county and state should be enough. If you're not in a metaliferous area, less likely to ge metal. But the rock itself appears to be more of a cobble: a large water-worn stone eroded over time by being in a river bed. Was there a nearby river? Could this rock have once been in that river?

 

[sjb]

We found the rock on a beach on Block Island RI- salt water for sure. The residue definitely rubs off easily, you just have to handle it to see gray on your hands and if you use the rock like a pencil, it writes like one. The vein looks like quartz, but as you saw, something else. I don't know if that vein is what is causing such a ruckus with the metal detector or the rock itself.

Thanks for your input!

 

[wwwtimmcp]

I get rocks with iron in them that drive my jw fishers pulse 8 crazy. it looks like a rock grew around a piece of iron nail.

 

[HISPAN]

It seems that the rock has adhered to the quartz and gold .... very interesting.
H

 

[High Plains Digger]

I couldn't get the photo to enlarge so I am at a disadvantage here. I did see the white streak, and it could be calcite or any number of other things besides quartz. Could be psilomine (spelling?) as that is an iron ore and is a messy rock, but I suspect it wouldn't last long in the ocean. If this is that soft, how did it last? I vote with the others--let's see the inside. I don't know RI, but is the area in general known for mineralization? Loadstone is heavy with iron, but I don't know if you can write with it. Does it seem heavy for it's size?

 

[timekiller]

It looks like schist to me. I find it here on the coast sometimes.But never had a piece set my detector off. And can't mark paper with it. It does flake off in your hands though.Pics. of some I find the one I mounted a piece of coral & shell too.
Taker Care,
Pete,

 

[Tuberale]

Curiouser and curiouser. Perhaps a cobble from the beach at Block Island?

Still need to see the interior.

I still think this is probably gniess instead of schist. But that's still just a guess.

 

[BioProfessor]

And what a gniess piece of schist it is.

Sorry, couldn't resist.

Daryl

 

[Curious The George]

I've been using a Minelab Safari for about two years now. I have never seen it "signal gold". Exactly how did it do that?

 

[allen]

meteorite maybe?

 

[Tuberale]

meteorite maybe?

Highly unlikely. Black fusion crust, although thin, doesn't rub off.

 

[sjb]

I've been using a Minelab Safari for about two years now. I have never seen it "signal gold". Exactly how did it do that?

If you look at the legend scale, it points to GOLD and has a target number of 17-18. It is so strong that I have to turn the sensitivity down to 4 in order to have it not read "overload" - I posted a new photo to show you what it looks like when I scan the rock- the link http://i994.photobucket.com/albums/af66/sjbgarden/Rock/DSC_2680.jpg

It has never has read iron, in fact I had it set on coin/jewelry mode only, and cancel out iron all together. I live in the Boston area- we know Iron, really know iron. This is really a smooth silvery- but not like mica- not flaky at all. It really looks like graphite with specks of quartz - very sparkly in places (new photo link for color and close up http://i994.photobucket.com/albums/af66/sjbgarden/Rock/DSC_2687.jpg ). It does not appear to be magnetic.

Thanks for all your input- love to learn!

SJB

 

[sjb]

I couldn't get the photo to enlarge so I am at a disadvantage here. I did see the white streak, and it could be calcite or any number of other things besides quartz. Could be psilomine (spelling?) as that is an iron ore and is a messy rock, but I suspect it wouldn't last long in the ocean. If this is that soft, how did it last? I vote with the others--let's see the inside. I don't know RI, but is the area in general known for mineralization? Loadstone is heavy with iron, but I don't know if you can write with it. Does it seem heavy for it's size?

does this photo help? I don't understand how to upload them directly - my photo files are too big

http://i994.photobucket.com/albums/af66/sjbgarden/Rock/DSC_2684.jpg

sjb

 

[High Plains Digger]

Daryl--You crack me up. That is quite sophisticated rock humor, and I love it. I am glad you get out detecting and aren't sedimentary.

 

[timekiller]

The only other metamorphic/sedimentary rocks that look like yours I find here are Basalt the pics. below. But all are hard & do not write also very heavy like rock should be.The last two pics.(with the oyster shell stuck to it) are of graphite a piece I found at a colonial site not sure what they were doing with it maybe molding something hot I figured.But is very light weight for size,&does write on paper.Is yours light weight

 

[sjb]

The only other metamorphic/sedimentary rocks that look like yours I find here are Basalt the pics. below. But all are hard & do not write also very heavy like rock should be.The last two pics.(with the oyster shell stuck to it) are of graphite a piece I found at a colonial site not sure what they were doing with it maybe molding something hot I figured.But is very light weight for size,&does write on paper.Is yours light weight

it is not light, actually a bit heavy for it's size. We have found basalt before, it seems a bit lighter in color. It really does look like the color of graphite in a pencil. It does not flake, but rubs off, and if I scratch it with my nails, tiny pieces come of. It marks anything it touches easily. The area that looks like quartz flakes off easily and leave small pieces that look like sparkles. It really is all one color by appearance, but there are small areas of shiny material in them, not striated such as the photos you all have posted.

How do you compress your photos to post them directly?

The humor is cracking us up...

Thanks again!!!!!!!

SJB

 

[timekiller]

The only other metamorphic/sedimentary rocks that look like yours I find here are Basalt the pics. below. But all are hard & do not write also very heavy like rock should be.The last two pics.(with the oyster shell stuck to it) are of graphite a piece I found at a colonial site not sure what they were doing with it maybe molding something hot I figured.But is very light weight for size,&does write on paper.Is yours light weight

it is not light, actually a bit heavy for it's size. We have found basalt before, it seems a bit lighter in color. It really does look like the color of graphite in a pencil. It does not flake, but rubs off, and if I scratch it with my nails, tiny pieces come of. It marks anything it touches easily. The area that looks like quartz flakes off easily and leave small pieces that look like sparkles. It really is all one color by appearance, but there are small areas of shiny material in them, not striated such as the photos you all have posted.

How do you compress your photos to post them directly?

The humor is cracking us up...

Thanks again!!!!!!!

SJB

I don't know then.I'm out of ideas for now it's weighing on me Anyway Take Care.
Here are some of the Posters Pics.

 

[High Plains Digger]

Timekiller--do you have rocks in your head? Basalt is volcanic, absolutely, and that is written in stone. Just to keep the record straight and rock solid.


If it looks like schist, smells like schist, and feels like schist, it probably isn't schist if it writes on a paper plate. That is very perplexing.

Don't take it to the Geology department at the univeristy. They don't know sch.....uh,.....nothing. Too many books.

 

[High Plains Digger]

Timekiller: I did want to say that your coral/shell mounts look gneiss, even if they are on schist. Were you born in Rocky Mount, NC? Really, now, I did like the photos of your mounts. Interesting thing to do with the coral, etc.