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What rock matt black color high density medium hard ?
  
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User4242333




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PostPosted: Jun 23, 2021 07:28    Post subject: What rock matt black color high density medium hard ?  

What stone identify ?
- Matt black color. ( Even when polished.)
- High density and medium hard. You can carve it with Dremel tools.



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PostPosted: Jun 23, 2021 07:29    Post subject: Re: What rock matt black color high density medium hard ?  

Second photo.


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Bob Carnein




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PostPosted: Jun 23, 2021 08:25    Post subject: Re: What rock matt black color high density medium hard ?  

Unfortunately, the first step in identifying a smooth pebble or cobble is to break it. This gives you an idea of the texture, which can't readily be seen on the outside. Then, to identify most rocks with any certainty, a thin-section examination is needed. As it stands, this might be a piece of basalt or hornfels.
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SteveB




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PostPosted: Jun 23, 2021 10:27    Post subject: Re: What rock matt black color high density medium hard ?  

Bob Carnein wrote:
Unfortunately, the first step in identifying a smooth pebble or cobble is to break it. This gives you an idea of the texture, which can't readily be seen on the outside. Then, to identify most rocks with any certainty, a thin-section examination is needed. As it stands, this might be a piece of basalt or hornfels.


+1 to this, even reminds me of anthracite/jet/coal. River rocks are a pain to identify, it helps if you found it yourself and can return to the location where more samples should be found that you can do more destructive tests on or possibly even find a rock outcrop containing more of the same material in true context of its natural habitate. Its not “here’s a picture, what is it?” Start with the sticky post about posting “what is it” threads. Contains a heap of tests and information you should test and find because very few “rocks” can be identified by sight alone. You should do a few of those tests in order to provide more data.

Density should be measured. This stone looks fairly homogenous so a good density measurement will go a long way. “High density” is meaningless, it must be measured and will narrow possibilities a LOT there are very few minerals or rock that really are high density, along with an accurate hardness test(a specific number not “its hard”) Specific gravity and hardness measurements will be a combination fairly specific to a couple of minerals/rocks. The post is there for a reason.
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Peter Lemkin




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PostPosted: Jun 23, 2021 12:47    Post subject: Re: What rock matt black color high density medium hard ?  

I find the second photo quite strange. Why the other three objects - two of them made of wood, the other maybe stone [or amber or plastic or glass]? I have a nagging suspicion you believe in 'mineral magic or mineral healing'. That is your own reality if true; we don't believe that here, and don't discuss that kind of thing. We do help identify stones....and their asthetics if provided with sufficent information about the mineral.

The black one is not water worn, it was clearly shaped by a human who polishing it. As mentioned just above, you have to do some tests and some work to help us to help identify it. Nothing is easy, and as mentioned very few minerals can be unambiguosly identified by a photo alone. We get such requests regularly [two today] in which they expected photos and minimal information would get someone a positive identification....
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PostPosted: Jun 23, 2021 23:34    Post subject: Re: What rock matt black color high density medium hard ?  

"nagging suspicion you believe in 'mineral magic or mineral healing'. "
- I wrote I have polished them with Dremel tool and water sand paper (Mirka brand).
- I have made the smaller one as a inkstamp used in Japanese ink paintings a.k.a "Sumi-e" (red ink stamp to mark the maker signature of painting.)

"Why the other three objects - two of them made of wood, the other maybe stone [or amber or plastic or glass"
- What is this: 1st is a simple HB pen you draw with it, 2nd is a yellow quartz or such found when I was 5-year old and 3rd+4th are those black rocks that I use in Japanese sumi-e painting to grind ink and stamp paintings ? Confused.

"The black one is not water worn, it was clearly shaped by a human who polishing it."
- I wrote I have polished them in 1st post.
- Do you know *rock tumbling* with grits ?
- Search rock tumbler machine. Please for knowledge.
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PostPosted: Jun 23, 2021 23:43    Post subject: Re: What rock matt black color high density medium hard ?  

Yellow stone is not "plastic" or "amber".
No amber in Finland where I live.



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PostPosted: Jun 23, 2021 23:56    Post subject: Re: What rock matt black color high density medium hard ?  

It might be Hornfels.
When black stones were raw field finds they had similar small brown rust/sand deposits as in this photo.
That is before rock tumbling machine, dremeling and water sand papering it to smooth

Photo when searching "Hornfels".



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Peter Lemkin




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PostPosted: Jun 24, 2021 00:02    Post subject: Re: What rock matt black color high density medium hard ?  

You miss my point and prove it further with your last posts. There is NO NEED to have put other objects [except perhaps a meter or other measuring stick in the photo. Now you have posted a separate photo[s] of the cube. Do you want to know about the black rock or not. Perhaps you want to know how they make castelle pencils? I'm being sarcastic, but there was no need to put the other objects in the photo. It was distracting and made one suspicious. actually, here among ourselves we usually do not deal with polished rock, but natural crystals. We are willing to help new persons try to identify minerals or rocks, but you have to do you end of the work. So many come here with a photo and just say 'what is it?' and expect an answer. The tread has gone all over the place about pencils, a wood stamp and other things that have no bearing on the black polished mineral you said you wanted help with. If you want help, as has been mentioned, you need to provide density and hardness and perhaps some other test results.
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PostPosted: Jun 24, 2021 00:17    Post subject: Re: What rock matt black color high density medium hard ?  

Why do I need to post other measurements ?
The answer was already given= *Hornfels* as in 3rd post. I'm happy with that answer.

I will now move on and thank for that answer.
Without further moving away from the original post.
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PostPosted: Jun 24, 2021 04:49    Post subject: Re: What rock matt black color high density medium hard ?  

[quote="User4242333"]Why do I need to post other measurements ?

As I mentioned (obviously NOT clearly enough) Every rock ( which are composites of Minerals) as well as pure minerals have a specific density (specific gravity is the measurement), as well as a specifc Hardness value. These are universal for the material. You can find quartz all around the world for example and its hardness will ALWAYS be close to 6.5, and NEVER close to 1.0 or 9.0. So if a sample is tested to be 1.2 for example it is impossible for it to be Quartz. Yet geology throws up a number of rocks and minerals that can look like Quartz in a photo but that is useless to test or identify properly. Same with density. YOU claim its high density, by what measurement? As I said there are few truely High Density rocks or minerals making for a much shorter list of possibilities for what you have there.

It seems you are unwilling to listen or learn of put in a little effort yourself to get an accurate honest answer. Seeing your recent responses I suspect you want us to “identify” so you can point here as authentication while you sell it to an unsuspecting person falsely. You obviously have no interest in this hobby and didn’t read the forum rules. An certainly no interest in correctly identifying what you’ve shown. Its clearly NOT been shown where this came from (which can further narrow down what it Could be as well as what it Couldn’t. Its obviously been tumbled but I apologise for giving you the courtesy of assuming it was river worn/tumbled. Is probably only been tumbled up to maybe 400 or 200 grit (tumble myself) but this is out of scope for the forum so I encouraged you to return to the location where more samples could be found so more information could be gleamed. Posing a sample with other samples as other point out speak more to youre character and intent and have less than zero to the task of identification. It could even be man made garbage thats been tumbled. Specific gravity and hardness testing will get you 90% of the way to an accurate identification, just settling for what it “looks” like is meaning less, the world is full of black or dark grey rocks as well as garbage so enjoy your pet rock but it doesnt really belong here.
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PostPosted: Jun 24, 2021 05:53    Post subject: Re: What rock matt black color high density medium hard ?  

You have a fine-grained dark rock. That's about all we know. If you broke it open and showed us the inside, perhaps we could get more specific. It could be a hornfels as you say but it could be a bunch of other fine-grained dark rocks. If you want more info we suggest you go to a local rock shop, rock/mineral club, or geology department.

Thinking about such rocks is not really what we do here; we are interested in natural crystalline material that shows natural crystal faces. We do try to help people like you but you just won't get much ready discussion about a polished dark fine grained rock here.

I think we should all just leave this thread at that. Good luck.
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