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Elise
Joined: 22 Dec 2009
Posts: 243
Location: New York State
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Posted: Dec 17, 2015 14:51 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Look what's on the 2016 15th Annual Westward Look Mineral Show poster - it features a 49-mm-tall heliodor crystal from the Yellow Water Mine in Tajikistan; photographed by Joe Budd (shared with permission from Dave Waisman)!
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15th Annual Westward Look Mineral Show poster. Photo: Joe Budd |
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17059 Time(s) |
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_________________ Elise Skalwold |
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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Posted: Nov 11, 2019 15:46 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Hello.
I have in my quartz sub-collection two small crystals, coming from the same locality, with a curious inclusion that resembles the screw dislocation.
The first one shows a tunnel with a geometrical "repetitive" pattern. Surprisingly the tunnel is open on both sides. I guess it is a sort of etching/dissolution that interested the included mineral (probably Siderite, which is often associated with Quartz from this locality).
The second one shows a small inclusion of possible Siderite with the same repetitive screw pattern, which needs to be magnified.
I would like to know the experts opinion.
Thanks in advance.
Best regards.
Sante
Mineral: | Quartz |
Locality: | Leoni Mountain, Sticciano, Roccastrada, Grosseto Province, Tuscany, Italy | |
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Dimensions: | 15,66 x 13,85 x 8 mm |
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Front view. The crystal has grown on C axis and the pattern is parallel to it. |
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14708 Time(s) |
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Mineral: | Quartz |
Locality: | Leoni Mountain, Sticciano, Roccastrada, Grosseto Province, Tuscany, Italy | |
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Dimensions: | 15,66 x 13,85 x 8 mm |
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14699 Time(s) |
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Mineral: | Quartz |
Locality: | Leoni Mountain, Sticciano, Roccastrada, Grosseto Province, Tuscany, Italy | |
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Dimensions: | 15,66 x 13,85 x 8 mm |
Description: |
The tunnel is open on both sides. |
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14706 Time(s) |
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Mineral: | Quartz, Siderite |
Locality: | Leoni Mountain, Sticciano, Roccastrada, Grosseto Province, Tuscany, Italy | |
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Dimensions: | 20 x 14 x 5 mm |
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The crystal has grown on A axis.The possible Siderite inclusion with screw pattern is neither parallel to the A axis nor to the C axis. |
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14706 Time(s) |
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Sante Celiberti
Joined: 04 Oct 2019
Posts: 699
Location: Tuscany
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Posted: Dec 21, 2019 17:44 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Hello.
Sorry, in the first picture's description of my previous post I erroneously wrote "parallel" instead of "perpendicular".
In this thread Mr. Duncan Miller said in 2011: "...so far I have not seen any images of these helical inclusions in quartz."; and Mr. Marco Campos-Venuti showed us, in 2014, his very beautiful quartz from Brasil.
Five years later I'd like to know the experts opinion about the attached specimens.
The first one is a Brasilian chalcedony geode. Looking for a nice goethite tuft in chalcedony, 15 years ago I came across this piece which at first sight I exchanged for faden quartz. Once at home, on closer inspection I realized that what I thought was a string was actually a spiral-shaped inclusion.
What attracted me to the small Chinese quartz was its strong iridescence due to internal fractures. Only later I noticed the small spiral-shaped inclusion inside it.
The third specimen is a Tuscan stalactitic chalcedony with a curious screw-formation. Also Mr. Campos-Venuti showed one. Has it anything to do with the helical-inclusion/dislocation theme?
Has knowledge of this intriguing topic progressed in recent years, just as Ms. Elise gave hope?
My best regards and wishes for coming holidays to all of you.
Sante
Mineral: | Quartz (variety chalcedony), Quartz |
Locality: | Barros Cassal, Rio Grande do Sul, Brazil | |
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Dimensions: | 48,8 x 38,2 mm |
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Both terminations of quartz crystal are attached to the walls of the geode. |
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14479 Time(s) |
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Mineral: | Quartz (variety chalcedony), Quartz |
Locality: | Barros Cassal, Rio Grande do Sul, Brazil | |
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Dimensions: | 48,8 x 38,2 mm |
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A close up of spiral-shaped inclusion. What kind of inclusion? It looks very similar to "flakes" on polished surface of chalcedony. Might it be crystobalite (quartz after crystobalite)? |
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14490 Time(s) |
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Mineral: | Quartz (variety chalcedony), Quartz |
Locality: | Barros Cassal, Rio Grande do Sul, Brazil | |
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Dimensions: | 48,8 x 38,2 mm |
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Other view of spiral-shaped iclusion. Can we call it "helical" inclusion? |
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14475 Time(s) |
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Mineral: | Quartz (variety smoky and variety scepter) |
Locality: | Leshan Prefecture, Sichuan Province, China | |
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Dimensions: | 18 x 12 mm |
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Front view where you can see a screw-shaped small inclusion. |
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14477 Time(s) |
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Mineral: | Quartz (variety smoky and variety scepter) |
Locality: | Leshan Prefecture, Sichuan Province, China | |
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Dimensions: | 18 x 12 mm |
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Side view where you can see the spiral-shaped inclusion. Is it actually an inclusion or a "large scale" helical dislocation? |
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14470 Time(s) |
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Mineral: | Quartz (variety chalcedony), Quartz |
Locality: | Monterufoli, Pomarance, Pisa Province, Tuscany, Italy | |
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Dimensions: | 114 x 105 mm |
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The Chalcedony stalactite size is 60 mm. |
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14473 Time(s) |
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Mineral: | Quartz (variety chalcedony), Quartz |
Locality: | Monterufoli, Pomarance, Pisa Province, Tuscany, Italy | |
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Dimensions: | 114 x 105 mm |
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Close up of the spiral-shaped formation. Pure randomness or we can suspect a relation with the helical (dis)location? |
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14501 Time(s) |
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Bob Carnein
Joined: 22 Aug 2013
Posts: 328
Location: Florissant, CO
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Posted: Jul 02, 2023 18:25 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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I recently purchased this specimen of topaz from the Shigar Valley, Gilgit-Baltistan, Pakistan. It has a helical fracture that can be seen clearly when viewed through one of the inclined prism faces (the basal pinacoid is frosted). The helix is "decorated" with tiny alternating fractures that look like the paddles on a commercial paddle stirrer. In one photo, they look black because of reflection in that direction. I am including it here because topaz crystals with helical "inclusions" seem to be pretty scarce, unlike beryls.
Mineral: | Topaz |
Locality: | Shigar District, Gilgit-Baltistan (Northern Areas), Pakistan | |
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Dimensions: | 3.9x2.4x2.3 cm. |
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Topaz crystal exhibiting helical fracture. |
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3905 Time(s) |
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Mineral: | Topaz |
Locality: | Shigar District, Gilgit-Baltistan (Northern Areas), Pakistan | |
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Dimensions: | length is about 2.4 cm. |
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Close-up of helical fracture system in topaz. |
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3905 Time(s) |
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John S. White
Site Admin
Joined: 04 Sep 2006
Posts: 1295
Location: Stewartstown, Pennsylvania, USA
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Posted: Jul 03, 2023 05:44 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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I must take issue with two comments by Mr. Carnein in his post with the photos of a topaz crystal with helical inclusions. I do not believe the inclusions are "fractures." Instead I believe they are the product of helical dislocations. Additionally I do not believe that such inclusions are rare with topaz crystals. I had a collection of crystals with helical inclusions and those in topaz far outnumbered those in beryl so I would consider them relatively common.
_________________ John S. White
aka Rondinaire |
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Bob Carnein
Joined: 22 Aug 2013
Posts: 328
Location: Florissant, CO
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Posted: Jul 03, 2023 11:09 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Thanks to Mr. White for his comments. To me, growth dislocations produce what look like fractures--they even have conchoidal markings on their surfaces. Perhaps "fracture" is an inaccurate term, but the dislocations apparently produce stress that results in a thin surface of dislocation. Perhaps this is a semantic quibble.
With regard to Mr. White's second comment, I was speaking from my personal experience. I have 2 beryl crystals with helical dislocations in my own collection and have seen several others offered for sale at shows. However, I have not seen similar topaz crystals personally, and I have only seen a few on Internet sites--including the FMF Forum. No doubt, Mr. White has more experience with these "inclusions" in topaz--I congratulate him for being fortunate enough to own several such crystals! BTW, I don't like the word "inclusions" for these fascinatng structures because, to me, the term implies the presence of some foreign material. The helical structures in my crystal appear to be empty.
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John S. White
Site Admin
Joined: 04 Sep 2006
Posts: 1295
Location: Stewartstown, Pennsylvania, USA
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Posted: Jul 04, 2023 08:52 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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I no longer have my collection of crystals with spiral inclusions but it consisted of three beryls, six spodumenes and seven topazes. Under high magnification one can see that at least one of them, a beryl from Brazil, does not consist of fractures. in fact, none of them do.
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_________________ John S. White
aka Rondinaire |
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John S. White
Site Admin
Joined: 04 Sep 2006
Posts: 1295
Location: Stewartstown, Pennsylvania, USA
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Posted: Jul 04, 2023 09:00 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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I should say that the inclusions in beryl photo I posted seem to be atypical. Those in a topaz from Mason County, Texas, are far more typical. See attached photo.
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3749 Time(s) |
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_________________ John S. White
aka Rondinaire |
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Bob Carnein
Joined: 22 Aug 2013
Posts: 328
Location: Florissant, CO
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Posted: Jul 04, 2023 09:06 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Those don't look at all like the structures in my topaz. I'll try to get a better photograph, but I admit that I'm challenged in that department.
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Bob Carnein
Joined: 22 Aug 2013
Posts: 328
Location: Florissant, CO
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Posted: Jul 04, 2023 11:08 Post subject: Re: Inclusions of spiral or helical growth and screw dislocations - (0) |
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Bob Carnein wrote: | Those don't look at all like the structures in my topaz. I'll try to get a better photograph, but I admit that I'm challenged in that department. | Here are a couple photos of the helical structure in my topaz from Pakistan.
Mineral: | topaz |
Locality: | Shigar Valley, Shigar District, Gilgit-Baltistan (Northern Areas), Pakistan | |
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Dimensions: | 1.5 cm. long |
Description: |
Close-up of helical structure parallel to "c" axis in topaz crystal |
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3732 Time(s) |
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Mineral: | topaz |
Locality: | Shigar Valley, Shigar District, Gilgit-Baltistan (Northern Areas), Pakistan | |
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Dimensions: | 1.5 cm. long |
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Close-up of helical structure parallel to "c" axis in topaz crystal. |
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3726 Time(s) |
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Mineral: | topaz |
Locality: | Shigar Valley, Shigar District, Gilgit-Baltistan (Northern Areas), Pakistan | |
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Dimensions: | 1.0 cm. long |
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Close-up of "paddle"-like fractures on helical structure parallel to "c" axis in topaz. |
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3726 Time(s) |
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