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Post by christopherl1234 on May 20, 2019 16:03:52 GMT -5
Amethyst with cocaxenite is another one of my favorites. I noticed lately that there has been some discussions that it is actually goethite that is the inclusion. I agree that there is most likely goethite in it....the black...but I am hard pressed to agree that the golden needles are anything but cocaxenite....the photos I have seen of cocaxenite are pretty convincing...but hey....I do not have a piece of paper saying I am a geologist or mineral specialist....so go figure   20150545 by CHRISTOPHER LESSO, on Flickr |
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Post by rockjunquie on May 20, 2019 16:09:41 GMT -5
That is BEAUTIFUL! Love the cut! It looks so fluid.
So- what is the white?
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Post by christopherl1234 on May 20, 2019 16:23:18 GMT -5
I am not sure what the white is probably just white quartz...they call it super seven also because they say there are seven different minerals in it
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Post by Pat on May 20, 2019 16:27:07 GMT -5
That is also one of my favorites! Thanks!
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Deleted
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Post by Deleted on May 20, 2019 17:15:21 GMT -5
I agree, it can be beautiful stuff, but the mineral lists of "7" claimed by the marketers are almost always wrong. First of all, 3 of them are just colors of quartz (amethystine, smoky and clear). The cacoxenite and rutile are goethite needles. Any red in these claimed as lepidocrocite turns out to be goethite or hematite. So basically, it is quartz with a mix of 1 or 2 iron oxide inclusions - "Super 2" or "Super 3"? Zooming in, to me it looks as if the white may be a perimorph of some of the goethite (i.e., some of the goethite needle-like formations within the quartz have dissolved away, leaving microscopic voids/veils with a white appearance). And yes, great job on the cab - the freeform shape really accentuates the internal pattern!
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gemfeller
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Member since June 2011
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Post by gemfeller on May 20, 2019 20:19:41 GMT -5
I like that cab and material a lot. I'm also intrigued by the cacoxenite vs goethite discussion. I have some chunks I'm trying to figure out how to slab correctly so the needles exhibit slight chatoyance.
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Deleted
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Post by Deleted on May 20, 2019 21:09:30 GMT -5
I'm also intrigued by the cacoxenite vs goethite discussion. I like it, too (actually anything with needles, cubes or other interesting inclusions). If I'm recalling the back and forth on mindat and other boards, the conclusion was that the Brazilian "super 7" material was quartz with iron content, resulting in both the goethite and/or hematite inclusions and amethystine color (the smoky areas was caused by radiation), and that the other claimed minerals just weren't present (cacoxenite is an iron-aluminum phosphate not known to occur in amethyst, rutile is titanium dioxide, and lepidocrocite is a ferric hydroxide unknown to occur in quartz anywhere near the area where the stuff was found). As far as I can recall, cacoxenite has never been confirmed to occur in gem material - more like crystal clusters in vugs in phosphorous-rich pegmatite and magnetite. Closest to gem material in which it's been found is in sedimentary chert, which, because those are opaque, cannot really show off the golden needle balls and sprays. |
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Post by hummingbirdstones on May 20, 2019 22:10:15 GMT -5
Beautiful cab, Christopher! Also one of my favorites. Cocaxenite or goethite, who cares? It's pretty no matter what it's called.  |
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julieooly
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Member since October 2018
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Post by julieooly on May 21, 2019 7:04:19 GMT -5
Agreed!! I'm wondering if I should start learning all the mineralology!
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Post by MsAli on May 21, 2019 7:15:04 GMT -5
One of my favorites and the photo is stunning but I better that's one you for sure have to see to really get how beautiful it is
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Deleted
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Post by Deleted on May 21, 2019 11:50:48 GMT -5
One of my favorites and the photo is stunning but I better that's one you for sure have to see to really get how beautiful it is Yeah, photos don't give a good idea of the almost metallic golden flashes and shimmer. Even videos don't give the full effect of this and other stones with similar optical phenomena (sheen obsidian, sunstones, larvikite, iris agate, cat's eyes and stars, etc.) - nothing better than seeing in person. |
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Post by MsAli on May 21, 2019 13:14:40 GMT -5
One of my favorites and the photo is stunning but I better that's one you for sure have to see to really get how beautiful it is Yeah, photos don't give a good idea of the almost metallic golden flashes and shimmer. Even videos don't give the full effect of this and other stones with similar optical phenomena (sheen obsidian, sunstones, larvikite, iris agate, cat's eyes and stars, etc.) - nothing better than seeing in person. Absolutely agree with you on that! |
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Post by vegasjames on May 21, 2019 17:15:16 GMT -5
Really nice.
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