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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
Posts: 1459
Location: Cambridge
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James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1459
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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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Dec 10, 2023 11:24 Post subject: Re: I want to know the sample |
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Stone weight = 3.53
Weight of stone in water = 1.38
Density = 2.55
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James Catmur
Site Admin
Joined: 14 Sep 2006
Posts: 1459
Location: Cambridge
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| Posted: Dec 11, 2023 03:49 Post subject: Re: I want to know the sample |
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Quartz is:
Hardness: 7
Specific Gravity: 2.65 (you measured 2.55, but it may contain some residual matrix / air bubbles)
Agate is hardness about 6.5
Could well be quartz
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