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coril
Joined: 23 Mar 2021
Posts: 5
Location: London
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 Posted: Mar 23, 2021 07:53 Post subject: what stones are these? |
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Can anyone tell by looking at them what type of mineral that could be?
Many thanks!
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Tobi
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Joined: 07 Apr 2009
Posts: 4235
Location: Germany
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| Posted: Mar 23, 2021 08:05 Post subject: Re: what stones are these? |
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| coril wrote: | Can anyone tell by looking at them what type of mineral that could be?
Many thanks! |
Well, by looking at them I can tell you that these are white rocks ;-)
Please read https://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487 and then please try to provide some further information.
Thanks
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ALshawani
Joined: 08 Feb 2020
Posts: 38
Location: Africa
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| Posted: Mar 23, 2021 08:15 Post subject: Re: what stones are these? |
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| I see it as unfinished opal
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vic rzonca
Joined: 18 Nov 2008
Posts: 820
Location: MA
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| Posted: Mar 23, 2021 08:31 Post subject: Re: what stones are these? |
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| Limestone.
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Volkmar Stingl
Joined: 23 Sep 2012
Posts: 983
Location: Innsbruck
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| Posted: Mar 23, 2021 08:34 Post subject: Re: what stones are these? |
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| ALshawani wrote: | | I see it as unfinished opal |
I disagree. I see a crystallized texture, with nearly isometric grains of same size. If the hardness is low and acid testing shows a carbonate, then I would say calcite or dolomite marble!
Volkmar
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James Catmur
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Location: Cambridge
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| Posted: Mar 23, 2021 08:44 Post subject: Re: what stones are these? |
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The answer really has to be 'no'. By looking all we can just say is 'white beads'.
Please do some tests (i.e. 7 and 8) and we might have an idea. If you put vinegar on them do you see bubbles?
| coril wrote: | Can anyone tell by looking at them what type of mineral that could be?
Many thanks! |
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vic rzonca
Joined: 18 Nov 2008
Posts: 820
Location: MA
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| Posted: Mar 23, 2021 09:39 Post subject: Re: what stones are these? |
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| I should have said a carbonate.
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coril
Joined: 23 Mar 2021
Posts: 5
Location: London
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| Posted: Mar 23, 2021 11:56 Post subject: Re: what stones are these? |
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| Thanks for all the interesting answers. I will try putting some vinegar on them once I get home. No one mentioned granite which is what came to my mind but I am no expert. Could it be granite or am I completely off here?
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Volkmar Stingl
Joined: 23 Sep 2012
Posts: 983
Location: Innsbruck
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| Posted: Mar 23, 2021 12:14 Post subject: Re: what stones are these? |
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| For sure not granite.
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coril
Joined: 23 Mar 2021
Posts: 5
Location: London
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| Posted: Mar 23, 2021 12:50 Post subject: Re: what stones are these? |
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| What makes you think so? Is it the colour?
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Pete Richards
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Joined: 29 Dec 2008
Posts: 842
Location: Northeast Ohio
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| Posted: Mar 23, 2021 13:09 Post subject: Re: what stones are these? |
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I agree that it's not granite, and it's due to the lack of color, or at least the lack of color variety. Granite has quartz, which is usually transucent grey, feldspar which can be white or pink, and almost always mica, which is silvery shiny plates that may be colorless to almost black. Often some other dark minerals as well.
It is the monotonous uniform white of these beads that says it's not granite - and rules out most other rock types as well.
_________________
Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Volkmar Stingl
Joined: 23 Sep 2012
Posts: 983
Location: Innsbruck
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| Posted: Mar 23, 2021 13:18 Post subject: Re: what stones are these? |
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| coril wrote: | | What makes you think so? Is it the colour? |
The beads consist obviously of only one mineral (most likely a carbonate, as Vic said). Also the texture points to a metamorphic carbonate (marble) with its homogeneous appearance.
Granite always consists of at least quartz, feldspar and mica, which also may differ in their color, size and orientation.
Volkmar
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coril
Joined: 23 Mar 2021
Posts: 5
Location: London
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| Posted: Mar 24, 2021 07:34 Post subject: Re: what stones are these? |
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So I popped one of those little guys into vinegar and it turned into a bubbly affair quite quickly. I guess that eliminates much of the possibilities of what it could be?
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Volkmar Stingl
Joined: 23 Sep 2012
Posts: 983
Location: Innsbruck
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| Posted: Mar 24, 2021 09:21 Post subject: Re: what stones are these? |
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| Seems to be calcite marble.
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coril
Joined: 23 Mar 2021
Posts: 5
Location: London
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| Posted: Mar 25, 2021 08:50 Post subject: Re: what stones are these? |
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| thanks for your help! the vinegar test was a really good idea, but i wouldn't have thought of it myself :)
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