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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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 Posted: Dec 05, 2023 15:16 Post subject: I want to know the sample |
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Hello everyone, I want help identifying this stone, knowing that it scratches the agate
| Mineral: | unknown |
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Dec 06, 2023 02:39 Post subject: Re: I want to know the sample |
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Hello.
If you cannot test the hardness, try testing the gravity.
On such a homogeneous material it should not be difficult.
The hexagonal prismatic habit is a further indication.
An -at least approximate- locality would be helpful.
Best wishes.
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 07, 2023 15:24 Post subject: Re: I want to know the sample |
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Welcome
Thank you for replying
In terms of hardness, I tried scratching the agate and it was easily scratched, which means that the hardness is above 7. In terms of location, it is North Africa, northwest of Libya.
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Dec 07, 2023 18:31 Post subject: Re: I want to know the sample |
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Beryl?
Habit, lustre, colour could fit.
But, with no further tests, just a guess...
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Bob Morgan
Joined: 18 Jan 2018
Posts: 233
Location: Savannah, Georgia
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| Posted: Dec 07, 2023 18:40 Post subject: Re: I want to know the sample |
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| Perhaps this is Libyan Desert glass. But I don't think such is as hard as agate.
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Matt_Zukowski
Site Admin
Joined: 10 Apr 2009
Posts: 718
Location: Alaska
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| Posted: Dec 07, 2023 19:27 Post subject: Re: I want to know the sample |
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I don't see any reason to assume that these rocks are mono-mineralic. It looks like some sort of clastic rock or corroded igneous rock with a coating of cryptocrystaline quartz on one side. I am not sure that the hardness really is >7; hardness tests can be hard to interpret with anything close to friable or with materials of similar hardness. I would be doubtful if you can get anything definitive from us with the information provided. I recommend that you find a geology club, or better a geology department of a nearby university, to identify what you have.
Good luck.
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lluis
Joined: 17 Nov 2006
Posts: 715
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| Posted: Dec 08, 2023 02:55 Post subject: Re: I want to know the sample |
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Just a guess from what Matt said before...
Maybe lechatelierite (fused sand by a lightning)?
Seems that there is some hole, and that are tubes of fused sand recovered with original sand... That could may scratch chalcedony (the surrounding sand, I mean)
Just quartz may look that scratches quartz...
Hope it serves
Lluís
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James Catmur
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Joined: 14 Sep 2006
Posts: 1396
Location: Cambridge
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| Posted: Dec 08, 2023 05:46 Post subject: Re: I want to know the sample |
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| Agate is not as hard as quartz, so assume >6.5
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lluis
Joined: 17 Nov 2006
Posts: 715
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| Posted: Dec 08, 2023 05:54 Post subject: Re: I want to know the sample |
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Then, lechatelierite coated by sand (quartz) would fit perfectly with scratching and shape...
Lluís
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Dec 08, 2023 07:49 Post subject: Re: I want to know the sample |
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| Lechatelierite seems to be the most likely identification, although I'm unable to reconcile the apparent and frequent hexagonal prismatic habit with the amorphous structure of Libyan dessert glass.
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James Catmur
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lluis
Joined: 17 Nov 2006
Posts: 715
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| Posted: Dec 08, 2023 10:13 Post subject: Re: I want to know the sample |
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Ciao, Santi
Maybe I am wrong, but Libyan glass is due to an impact and lechatelierite is due to electricity.
Not same in origin, although all being at end fused quartz...
Lechatelierite is roundish, and use to have a hole in any place. As I see in this case.
I fail to see hexagonal shapes (maybe forcing my slight imagination.....). But cylindrical fits more with my mental schemes... Maybe sorry, but is what I see..
With best wishes
Lluís
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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| Posted: Dec 08, 2023 12:43 Post subject: Re: I want to know the sample |
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Ciao, LLuis.
Of course, the cylindrical shape, common in these stuffs, is evident.
Nonetheless, I seem to see, amongst the shown material, at list three pieces with a coarse hexagonal shape. The same I seem to see in 1st and 7th photo on Mindat (Lechatelierite).
But perhaps this is due to my imagination or, more likely, to my maculoopathy.
Warm greetings.
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 08, 2023 16:23 Post subject: Re: I want to know the sample |
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| Such as what tests are required
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 08, 2023 16:25 Post subject: Re: I want to know the sample |
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| Sante Celiberti wrote: | Beryl?
Habit, lustre, colour could fit.
But, with no further tests, just a guess... |
Such as what tests are required
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 08, 2023 16:46 Post subject: Re: I want to know the sample |
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| Bob Morgan wrote: | | Perhaps this is Libyan Desert glass. But I don't think such is as hard as agate. |
It is not Libyan desert glass. I know desert glass well and it is found in sandy areas and on the surface of the earth.... And this stone of ours is found attached to the marble rocks, and I will attach pictures of the enclosures.
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James Catmur
Site Admin
Joined: 14 Sep 2006
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James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1396
Location: Cambridge
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| Posted: Dec 09, 2023 07:04 Post subject: Re: I want to know the sample |
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| Quartz replacement of fossils? Test for density, please
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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| Posted: Dec 09, 2023 13:21 Post subject: Re: I want to know the sample |
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| ALshawani wrote: | | Such as what tests are required |
I would say that the first thing is to discern between siliceous or carbonate material. Perhaps you can repeat the hardness test by trying to scratch a bottle glass better than a piece of rough agate. After dragging/pressing a sharp edge of the unknown onto the glass, wipe it with your finger and look for a permanent scratch.
If the result of this test is negative, place a drop of dilute hydrochloric acid on a sample and check for effervescence.
A specific weight test must be done very carefully (Archimedes method) to be reliable.
Anyway in this case it would not be helpful as density of calcite and quartz is similar so the result would not be conclusive.
BTW, which size is the larger stone in first photo?
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 10, 2023 10:41 Post subject: Re: I want to know the sample |
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| James Catmur wrote: | | Quartz replacement of fossils? Test for density, please |
Yes, I will measure the density
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