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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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 Posted: Jul 24, 2012 11:56 Post subject: Re: Strange Quartz found In New York |
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| John S. White wrote: | | ...dark purple and black, are not characteristic for rutile... |
Hi John. When you say black is an uncharacteristic color for rutile, would you say it is just uncommon or a rarity. I have some quartz with black rutile. What could cause the black color? Perhaps oxidation?
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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John S. White
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Joined: 04 Sep 2006
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Location: Stewartstown, Pennsylvania, USA
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| Posted: Jul 24, 2012 20:54 Post subject: Re: Strange Quartz found In New York |
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Rutile can be impure, it is known to contain up to 10% iron which I would guess can make it quite black in massive crystals, but I would expect needle-like crystals to be lighter in color.
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John S. White
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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| Posted: Jul 25, 2012 02:25 Post subject: Re: Strange Quartz found In New York |
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| John S. White wrote: | | Rutile can be impure, it is known to contain up to 10% iron which I would guess can make it quite black in massive crystals, but I would expect needle-like crystals to be lighter in color. |
Thanks for the reply John. I see on internet jet black rutile needles in clear quartz from India. It does not look like rutile to me; could it perhaps be schorl?
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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John S. White
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Location: Stewartstown, Pennsylvania, USA
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| Posted: Jul 25, 2012 04:09 Post subject: Re: Strange Quartz found In New York |
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That is very likely. I am unaware of any locality for rutilated quartz in India.
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John S. White
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J. Lawsonite
Joined: 25 Sep 2012
Posts: 1
Location: Upstate, ny
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| Posted: Sep 25, 2012 13:36 Post subject: Re: Strange Quartz found In New York |
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| I have a strong feeling that the "fibrous" mineral inclusion that you see is hematite, less likely but still possible. it is another iron oxide of some sort e.g. goethite.
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 5047
Location: Barcelona
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| Posted: Sep 25, 2012 15:07 Post subject: Re: Strange Quartz found In New York |
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| J. Lawsonite wrote: | | ....it is another iron oxide of some sort e.g. goethite. |
I agree, I would vote for Goethite.
Adam, could you check if the color of the needles changes according its position from black to yellowish-brown? The Goethite is pleochroic....
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Pete Richards
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Joined: 29 Dec 2008
Posts: 845
Location: Northeast Ohio
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| Posted: Sep 25, 2012 15:51 Post subject: Re: Strange Quartz found In New York |
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| J. Lawsonite wrote: | | I have a strong feeling that the "fibrous" mineral inclusion that you see is hematite, less likely but still possible. it is another iron oxide of some sort e.g. goethite. |
I've never heard of fibrous hematite. Hematite usually forms platy pseudo-hexagonal crystals, or botryoidal masses composed of gazillions of crystals all packed together. But not separate fibers.
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Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Jordi Fabre
Overall coordinator of the Forum
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Location: Barcelona
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| Posted: Sep 25, 2012 16:11 Post subject: Re: Strange Quartz found In New York |
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Two examples of needles / sprays of Goethite inside Quartz from Morocco
| Description: |
Quartz with Goethite
Tizirine, Tizi n'Tichka, Ouarzazate Morocco
Main crystal size: 1.8 × 1.3 cm. |
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16456 Time(s) |
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| Description: |
Quartz with Goethite
Tizirine, Tizi n'Tichka, Ouarzazate Morocco
Main crystal size: 1.8 × 1.3 cm. |
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| Viewed: |
16428 Time(s) |
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Carl
Joined: 07 May 2009
Posts: 28
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| Posted: Sep 26, 2012 21:41 Post subject: Re: Strange Quartz found In New York |
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The analysis that NYSAM did back in the late 1990s on this material was that it was an amphibole; likely riebeckite. I have several pieces where the amphibole crystals go from one quartz crystal, through open space, and into another quartz crystal.
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