Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Here are a couple pics of gilalite in quartz I picked up in Tucson. The material is found in the Paraiba district of Brazil. The first is typically what one sees in this sort of specimen, clear quartz with floating discs of gilalite, often referred to as Medusa Quartz or hyperbolized as "Paraiba Quartz" . Taken with fiber optic light, not dark field:
When these discs are viewed sideways, you can see where the name "medusa" quartz comes from:
Here is a specimen of quartz with fibrous gilalite disseminated throughout the entire specimen: Also shot with fiber optic light.
Last edited by Barbra Voltaire, FGG on Thu Mar 11, 2010 10:46 pm, edited 4 times in total.
Joined: Wed Nov 15, 2006 9:44 pm Posts: 1079 Location: Washington State
Those are really neat images Barbra. I always wonder how these minerals can form as they do, just floating on the middle of something with a completely different chemistry and structure. It's really kind of magical.
Those are really neat images Barbra. I always wonder how these minerals can form as they do, just floating on the middle of something with a completely different chemistry and structure. It's really kind of magical.
There's an article on the net http://www.yourgemologist.com/ISGForums ... php?t=6173, that says that gilalite in quartz is a faked composition of quartz and glasses, clear and blue. It explains how to do this and links Barbra's pics on this GO thread as an 'illustration' of it's proposition. I thought that some pics that show clearly the acicular habit of the gilalite at stages of magnification sufficient to show no manipulation might sufficiently discredit that outside post and its implications. Don't think you can fake 'acicular' by blobbing molten blue glass
Admin Note: These folks above have rethought their position after new evidence was presented to them. They have retracted their posts and articles.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
This woman PMd me directly a while back insisting that I never ran any tests on my material and it was actually glass.
I ran tests to verify and the specimens were indeed quartz. They are. G&G has articles on gilalite in qtz. My specimens were also purchased from Marco Campos Venuti.
Ms. Gringa is misinformed.....yet again. I doubt she ever physically tested the material; her conclusions were speculative based on misinformation and misinterpretation of photos. You will notice that there are NO verified examples of the faked up glass she speculates exist.
Other posters have corrected the misinformation on the link Kerensky provided.
Barbra, For some reason I can't see the third pic you posted. Broken link or....?
Yes, I also did the usual tests for doublet and came up with nothing untoward from my sample. Though I have not posted them here, in my records there is also photo-evidence of the following in the same stone, in addition to examples of a very pronounced acicular habit: - Medusa formation. - Scattering of the gilalite in depth, sufficient to make very unlikely any laying down of fake (or real) material on a prepared quartz base prior to sealing in under glass. - Similar scattering in depth of minute inclusions of one or more other types, including (I think) two phase inclusions.
Being suspicious of something new is one thing - but best to zip the mouth until one has some test results, no?
Those 'other inclusions' invite further exploration when I get around to it. They are small enough both to warrant some observation at > x150 mag and, insh'Allah, for me not to be too disadvantaged by not yet having upgraded my camera so I can use image stacking software
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Going to Tucson? That's where I got mine. It was purchased from Marco Campos Venuti. He is set up in a small room FILLED with bins of the most interesting inclusions you will ever see in one spot.
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