FMF - Friends of Minerals Forum, discussion and message board

[Lou B.]

Got at an estate auction and also a fossil.

[Lou B.]

Couple more pics when I tap it it kinda pings.

[Bob Harman]

I have no idea where your example was from and looking like a rock, I doubt any meaningful testing, other than seeing if the example reacts to acid (being a carbonate), could be of help.

Having said that, and based just on the photos, your example may be a fossiliferous limestone with several invertebrate fossils showing patchy pyritization. This is just a guess.
I suggest testing with acid or vinegar, at least to see if the basic rock is limestone. Bob

[Lou B.]

Does it matter what kind of vinegar and it looks like inside is black one of the pics you can see it.

[Lou B.]

Vinegar did nothing Apple cider

[Pete Richards]

Let's assume this is a metal, which seems reasonable given your observation of sounds and its general appearance. Metals generally are malleable; rocks and minerals are generally not. Hit a corner with a hammer several times. Does the corner flatten or does it shatter? If it flattens, it is a metal. If it shatters, it is a rock or mineral. Try scratching a flat area with a knife blade. Can you scratch it? If so, does the stuff that makes the scratch form a groove, or fall away as a powder? If a groove, it is a metal; if a powder, it is a mineral or rock.

If a knife won't scratch the specimen, it could still be a metal but would be a hard one.

You don't say how heavy it is. Ideally, you would estimate a specific gravity. But is it light, average, or heavy compared to a typical rock of the same size?

Just a note: testing this with acid may not prove much. Acid will make limestone fizz, but it will also make some metals fizz.

For further help, please tell us where you found it and in what setting, and try some basic tests as we are suggesting.

[Lou B.]

Chipped off feels heavier than a regular rock not much but it does. I got it at estate auction with this fossil. Sorry about the toes.

[Roger Warin]

What is the density?

[Lou B.]

I am a beginner what exactly do you mean. Its hard and it seems a bit heavier than a regular rock

[Bob Morgan]

You may have chalcedony. Such can make a high pitched clink somewhat metallic sounding.

[Peter Lemkin]

Here, I have to say I am disappointed in some regular members who did not tell our newbie about reading

https://www.mineral-forum.com/message-board/viewtopic.php?t=1936


This, I think, should ALWAYS be the first reply to most [not all] such requests. This person doesn't even know what asking to find the density means - and it is not his fault. I think it is doing somewhat of a diservice to not ask EVERY newbie to look at the various things they can do to report in greater and needed detail about what they are asking identification for. Part answers and guesses on the part of the 'old pros' is more likely to confuse and mislead than provide a satisfactory answer. Just sayin....... your milage may vary. Just my take.

[Vinoterapia]

I can assure you that your rock has no metal at all. It is simply a piece of limestone, and considering the texture of the surface, it was collected from a karst (cave) area. That ping that you hear is very characteristic of compact limestones, and sometimes from sandstones.

When I was young I was part of a speleo team and the sound that you describe is quite characteristic.

[Bob Harman]

About time someone replied (Vinoterapia) who knows what he is talking about and agrees with me in my very first response!
Otherwise several rather silly responses......a metal.....clearly not......."test the density" without replying telling the novice how and anyway density has limited use with rocks.....
Even the testing with "apple cider vinegar" was silly. Someone should have noted that and suggested full strength vinegar on a small piece; then there might have been carbonate (limestone) fizzing.

I hate to say this, but this thread and the recently locked thread where someone, not even from the US, suggested gold (!) in a Lower Michigan found rock are exactly why I have been increasingly limiting my responses in this forum.

People, especially local and regional folks, should be given first chance to respond when they really have an idea what they are talking about........ People from Europe and Australia either should really, really know about specific US finds or simply refrain from responding until locals give their opinion!

I'm outta here ! Bob Harman

[Roger Warin]

Does it change the direction of the compass needle?

[Vinoterapia]

Sorry, Bob, I see I did not make myself clear. Let me try again.

- The rock is a limestone.
- The surface of the rock show signs of dissolution/abrasion (water-worn) as seen in karst.
- Certain compact rocks produce a metallic sound when hit by a hammer.

Further tests:

Pulverize one of the chips and leave it overnight in vinegar. Does it get dissolved?
Hit the rock with a hammer and sniff at it. Does it smell like rotten eggs/sulfur?

If both answers are yes you have proven that you have a limestone sample.