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Roger Warin
Joined: 23 Jan 2013
Posts: 1232
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 Posted: May 16, 2015 09:53 Post subject: Re: Strange planes in quartz |
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Hi,
When I see such quartz, I think recognize the cleavage plane induced by shock or high mechanical pressures. This plane is {10-11}.
Of course afterwards these microfaults can be partially filled with calcite.
Roger.
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Pete Richards
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Joined: 29 Dec 2008
Posts: 843
Location: Northeast Ohio
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| Posted: May 16, 2015 18:14 Post subject: Re: Strange planes in quartz |
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| Josele wrote: | | Pete, I suppose you mean "... consistent with the a-axis of calcite ...", isn't it? |
Thank you, Josele. I did not express myself very clearly. I should have said that the striations are in orientations consistent with the three-fold symmetry of calcite. The striations were on pinacoid faces (0001) of the now-gone calcite, which are perpendicular to the c-axis and thus lie in a plane that is parallel to that defined by the a-axes. Whether the striations are traces of cleavage intersecting that plane or traces of mechanical twinning, they would in fact be parallel to the a-axes.
In the left drawings are calcite with the cleavage rhomb and the pinacoid, both standard clinographic and top views. On the right drawnings are calcite with the negative rhomb {01.2}, which is the mechanical twinning direction, and the pinacoid. In either case, the striations are parallel to the edges between the rhomb and the pinacoid; these are shown in black. The axes are shown in green and the crystal edges in red.
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Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Pete Richards
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Joined: 29 Dec 2008
Posts: 843
Location: Northeast Ohio
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| Posted: May 16, 2015 18:30 Post subject: Re: Strange planes in quartz |
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| Roger Warin wrote: | Hi,
When I see such quartz, I think recognize the cleavage plane induced by shock or high mechanical pressures. This plane is {10-11}.
Of course afterwards these microfaults can be partially filled with calcite.
Roger. |
Hi Roger,
I appreciate your comment and am familiar with the cleavage of quartz and with your interest in it. The cleavage plane set {10.1} is parallel to one of the two rhombohedra that typically form the terminations on quartz. In this specimen, one can locate multiple sets of incomplete terminations along specific edges of the quartz plates. None of the sets of grooves are aligned in one of theses directions. The main set is approximately parallel to a prism face, but deviates from parallelism by perhaps 5-10°. Neither of the other two sets is parallel to a rhombohedral face.
In addition, the cleaved quartz I am familiar with does not have multiple parallel cleavages - usually just one cleavage is present, and the cleaved fragment is broken free from the rest of the crystal. Sometimes a shard is bounded by two parallel apparent cleavage surfaces.
It is hard to see how this specimen could be cleaved multiple times, the fragments spread so there is space in between them, but left intact together for the calcite to later invade. Further complicating this theory is that the cracks never go all the way through the crystal - a core region remains intact. I think the detailed evidence rules out cleavage in this case.
Thanks for your interest.
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Collecting and studying crystals with interesting habits, twinning, and epitaxy |
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Josele
Joined: 10 Apr 2012
Posts: 410
Location: Tarifa, Spain
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| Posted: May 16, 2015 19:28 Post subject: Re: Strange planes in quartz |
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Great drawings! thanks for taking the job, without them it would have been difficult to understand. Then striations can have two very different origins, normal {101} and flat {012} rhombohedron can be involved. If it were possible measure the tilting angle of a stria wall...
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John S. White
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Joined: 04 Sep 2006
Posts: 1298
Location: Stewartstown, Pennsylvania, USA
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| Posted: May 17, 2015 05:00 Post subject: Re: Strange planes in quartz |
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Since this thread has taken on new life I felt I should try to produce a better photo of one of my Bor mine, Dalnegorsk, Russia, specimens. In some ways this specimen is very different from all of the others that I have seen. It still contains much of the calcite that is responsible for the "slices" in the quartz, concentrated at the base of the specimen. It is also responsible, I believe, for the odd termination. The quartz crystal is 11.5 cm long. This photo is an improvement, but it is far from the quality that I would like it to be.
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John S. White
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Jun 04, 2015 12:58 Post subject: Re: Strange planes in quartz |
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Hi Josele. I thought I saw these type of quartz growth before, but could not remember where. I found this crystal lying in my crystal room. Please correct me if it is not caused by the same growth interference as yours.
| Mineral: | Quartz |
| Locality: | | Orange river area, Kakamas, ZF Mgcawu District, Northern Cape Province, South Africa |  |
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| Dimensions: | 38 x 12 x 10 mm |
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| The crystal is milky to clear with a coating of iron oxide. |
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| Mineral: | Quartz |
| Locality: | | Orange river area, Kakamas, ZF Mgcawu District, Northern Cape Province, South Africa | |
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| Dimensions: | 38 x 12 x 10 mm |
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| Mineral: | Quartz |
| Locality: | | Orange river area, Kakamas, ZF Mgcawu District, Northern Cape Province, South Africa | |
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| Dimensions: | 38 x 12 x 10 mm |
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Jul 20, 2015 08:04 Post subject: Re: Strange planes in quartz |
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I had a chance to examine John's enigmatic quartz specimen last week and am completely fascinated by it and by this topic thread. This is just a quick photo taken with a handheld camera and doesn't show much of its surface features. Is this a series of separate crystals or is it a single crystal changing growth directions with each “plate” or is it a single crystal whose growth is “normal” internally, merely with surface distortions imposed on it by the calcite? I'm leaning toward the last, but the terminations in these various examples really are a conundrum. I did not have much time to study the specimen and now it is haunting me!
The second image shows the same features of equilateral triangles as Pete Richards discussed here: https://www.mineral-forum.com/message-board/viewtopic.php?p=45348&highlight=#45348
This is a similar specimen on Mindat: https://www.mindat.org/photo-296046.html
(John's original posting of the specimen: https://www.mineral-forum.com/message-board/viewtopic.php?p=45365&highlight=#45365 )
| Mineral: | Quartz |
| Locality: | | Bor Pit, Dalnegorsk B deposit, Dalnegorsk, Dalnegorsk Urban District, Primorsky Krai, Russia | |
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| Dimensions: | 5.5 cm |
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| Quartz, John S. White Collection (photo: Elise Skalwold) |
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| Close-up showing the surface. |
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Elise Skalwold |
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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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| Posted: Jul 28, 2015 16:44 Post subject: Re: Strange planes in quartz |
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This is another specimen from the same locality. Looking down the length, it appears as three or four hexagonal crystals, but internally it seems to be a single crystal. It also has a cluster of the thin blades near the base; I don't know if these are part of a single crystal or if they are separate crystals. Can anyone lend some insights into what the growth environment was like in order for these strange crystals to form (or what series of events resulted in this)? What is the geology of the Bor Mine area which led to this outcome?
| Mineral: | Quartz |
| Dimensions: | 85 x 25 x 25 mm |
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| Quartz, Bor Mine, Dalnegorsk, Russia (photo: Elise Skalwold) |
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12134 Time(s) |
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Elise Skalwold |
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Xueyan Jin
Joined: 19 Oct 2015
Posts: 11
Location: Jinan
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| Posted: Nov 04, 2015 00:57 Post subject: Re: Strange planes in quartz |
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The faces of the some Quartz crystals exhibit interesting and attractive growth interference patterns, look like to be carved, with some deep groove on matrix. But All are Natural! NO SAWN. The quartz clusters formed over hematite that often subsequently dissolves, leaving these groove in the quartz.
| Mineral: | Quartz |
| Locality: | | Jinlong Hill, Longchuan, Heyuan Prefecture, Guangdong Province, China | |
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| Dimensions: | 260g |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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| Posted: Nov 04, 2015 02:58 Post subject: Re: Strange planes in quartz |
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Hi Xueyan. How about a few more photos of this quartz?
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Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Xueyan Jin
Joined: 19 Oct 2015
Posts: 11
Location: Jinan
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| Posted: Nov 04, 2015 04:22 Post subject: Re: Strange planes in quartz |
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no problem^ ^
| Mineral: | Quartz |
| Locality: | | Jinlong Hill, Longchuan, Heyuan Prefecture, Guangdong Province, China | |
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| Dimensions: | 260g |
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11635 Time(s) |
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