CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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PostPosted: Tue Apr 28, 2009 3:34 pm 
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I'll take it to mean greater than or equal to...er opal?


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 Post subject: Re: Sunset Quartz
PostPosted: Sun Jul 21, 2013 3:30 am 
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Hi, i saw listed somewhere called 'Tangerine' quartz, similar color also orange so i am wondering this 'sunset' is also called 'Tangerine' quartz?


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 Post subject: Re: Sunset Quartz
PostPosted: Sun Jul 21, 2013 11:32 am 
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Tangerine quartz is colored by a thin coating of iron oxides which give it its brilliant orange color. These may or may not be covered by an additional layer of clear quartz, which of course imparts extra durability. Regardless, such material isn't suitable for facet rough.

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 Post subject: Re: Sunset Quartz
PostPosted: Sun Jul 21, 2013 3:19 pm 
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No wonder there are many 'tangerine' being sold online, i thought they are similar to 'sunset' :roll:


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 Post subject: Re: Sunset Quartz
PostPosted: Tue Jul 30, 2013 11:46 am 
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Dr. Hanneman,

Would Osidian or Moldavite have a higher SI content than quartz? just a guess but both have a lower SG

Curious.


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 Post subject: Re: Sunset Quartz
PostPosted: Tue Jul 30, 2013 12:13 pm 
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I'm not Dr. Hanneman, but my guess is no. Obsidian and moldavite are natural glasses cooled from molten rock--in obsidian's case, a component of rhyolitic magma, in moldovite's case a mixture of crustal rocks. Neither is pure silica (SiO2). In the case of obsidian, it is going to be a mixture largely of silica and feldspar, and with moldavite it's likely got even more stuff melted in. And, of course, if we're talking on a volume-by-volume basis, glass isn't arranged in an orderly crystal structure so it is less dense.

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 Post subject: Re: Sunset Quartz
PostPosted: Tue Jul 30, 2013 12:22 pm 
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It's my understanding that obsidian as approx 75% Si02 with the remainder being Mg and Fe oxides.
Oh, I'm not Dr. Hanneman either.


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 Post subject: Re: Sunset Quartz
PostPosted: Wed Jul 31, 2013 9:18 am 
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Thanks Scarodactyl and Barbara,

I don't have any info on % contents for any minerals, the only other candidate I could think of would be Coesite, not a gemstone though.

Hopefully Dr. Hanneman will shed some light, otherwise it will be like the color change Amethyst debate from some time ago, lost track of that one without the final coclusion.


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 Post subject: Re: Sunset Quartz
PostPosted: Wed Jul 31, 2013 3:13 pm 
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Stick with quartz. I have nothing to add. Those are good answers. Fused quartz has a lower specific gravity.


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