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 Post subject: Opal crystals
PostPosted: Mon Apr 24, 2023 2:00 pm 
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Attached are microscopic images of a boulder opal.
What are the crystals in this opal?


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File comment: Opal
320F8A32-828C-4920-AF2A-293B40366C45.jpeg
320F8A32-828C-4920-AF2A-293B40366C45.jpeg [ 330.49 KiB | Viewed 8676 times ]
File comment: Opal
504F3EBB-5E7B-49A0-B411-4F0D085C671B.jpeg
504F3EBB-5E7B-49A0-B411-4F0D085C671B.jpeg [ 376.62 KiB | Viewed 8676 times ]
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 Post subject: Re: Opal crystals
PostPosted: Tue Apr 25, 2023 3:05 pm 
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Hello. I don't see any crystals in these images. Boulder opal is typically in a cryptocrystalline hematite metrix so that is likely what you are seeing.

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 Post subject: Re: Opal crystals
PostPosted: Tue Apr 25, 2023 7:01 pm 
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Stephen Challener wrote:
Hello. I don't see any crystals in these images. Boulder opal is typically in a cryptocrystalline hematite metrix so that is likely what you are seeing.



And now?



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 Post subject: Re: Opal crystals
PostPosted: Fri Apr 28, 2023 1:26 pm 
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As Stephen said, the opal itself is not crystalline. However, opal has a habit of replacing other things, and it is possible there used to be crystals of something that the opal replaced. Opal is known to replace belemites (Australia), Wood (lots of places, but Nevada is a good example), cracks in stones (Spencer Idaho), interstices of sand (Louisiana, and recently, if reports are to be believed, Mississippi), Clams (also Australia), bones, teeth, shells (see Smithsonian article), etc.

If you are asking what kind of crystals were replaced by the opal, that is an interesting question, but one I can't help you with.


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 Post subject: Re: Opal crystals
PostPosted: Fri Apr 28, 2023 3:37 pm 
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And the simple answer is most likely to be OPAL. If it is actually Boulder Opal as claimed. The music in the video is quite soothing, the lighting effects are well done. But I agree it looks like some kind of opal replacement maybe a fern branch or similar. Its anybody's guess I suppose.

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