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Josele
Joined: 10 Apr 2012
Posts: 407
Location: Tarifa, Spain
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Posted: Nov 25, 2016 18:25 Post subject: Weird face in quartz |
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A friend brought me a small smoky quartz from Madagascar, bought in a road shop near Itremo. Although it is somewhat chipped, it retains some interesting features. In addition to the usual faces of the prism (m) and positive (r) and negative (z) rhombohedrons, the crystal shows what I suppose are two faces of the trigonal bipyramid (s), one of the trapezohedron (x) and another one that I can not recognize. Is a small scalene trapezium placed between adjacent x, s, r and m faces as can be seen in pictures.
Comments are welcome!
Thanks.
Mineral: | Quartz (variety smoky) |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Dimensions: | 7 cm |
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37939 Time(s) |
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Mineral: | Quartz (variety smoky) |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Dimensions: | FOV about 2.5 cm |
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37895 Time(s) |
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Mineral: | Quartz (variety smoky) |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Description: |
Face at reflex is a x-face. At his right a bigger s-face and over them the unknown face. |
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37889 Time(s) |
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Mineral: | Quartz (variety smoky) |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Description: |
Trying to reflect on each of the faces. Last photo shows the weird face at reflex. |
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38022 Time(s) |
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Pete Richards
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Posted: Nov 27, 2016 16:43 Post subject: Re: Weird face in quartz |
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Josele, you offer quite a puzzle! I think things are not as they seem, though I can't be sure. I note that the face that is in position to be the s face actually is not smooth, but concave and stepped - in your top-left image in figure 4 this is particularly apparent. Furthermore, I don't think its relationship to the other faces is right for an s face. The s face has the special property that it bevels rhombohedron and prism faces in both directions. This is to say that its opposite edges are parallel to each other in both directions, as can be seen in my first drawing and your second (excellent) image. I don't think the face in your fourth image shows this property, and I propose to ignore it as being not a true face, though I don't have a good explanation for why it is there. Perhaps contact with another crystal?
I suggest that there is no s face on this corner, and that the face illuminated in your figure 3 is an x face with indices (511). The mystery face appears to bevel x(511) and r(101). If so, its indices must be some linear combination of (511) and (101). I chose (511)+2*(101) or (713), which I arbitrarily named ∂. (713) is not a satisfying set of indices because they are too high (especially 7), but I don't think any combination of the indices of the two surrounding faces (i.e. (511) and (101) ) will produce a face that bevels the two and has satisfyingly low indices.
Further progress beyond this somewhat speculative analysis would require measurement of the angles between the various faces.
Hopefully this analysis is of some help in understanding your crystal!
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: Nov 28, 2016 02:56 Post subject: Re: Weird face in quartz |
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'Perhaps contact with another crystal? '
That is what it looks like to me too.
_________________ Pierre Joubert
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Josele
Joined: 10 Apr 2012
Posts: 407
Location: Tarifa, Spain
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Posted: Nov 28, 2016 19:02 Post subject: Re: Weird face in quartz |
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Pete, Pierre, thanks for your help.
After seeing Peter's drawings and spent some more time with the X10 loupe, now I see there is not a s-face in this corner as you pointed, definitely angles don't fit. Although to me it does not seem a contact rather a complex / distorted step followed by a slightly curved plane sub-parallel to the adjacent r-face. There is some other distorted corners at this specimen. Anyway, not a real face.
The supposed x-face really looks like a true x-face. Face is flat but it has the longest side of the triangle somewhat curve because prism face is curved at top.
And weird small face is a bevel between x and r faces, as showed in Peter's figures 4 and 5. Not a very common face!
Pete, I really envy your capability for recognizing faces and even for determining Miller indices (from photos!!!), congratulations and thanks for your patience sharing your knowledge in this didactic and profitable way.
Mineral: | Quartz |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Dimensions: | FOV: 2 cm |
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37557 Time(s) |
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Mineral: | Quartz |
Locality: | Itremo Massif, Itremo, Ambatofinandrahana District, Amoron'i Mania Region, Fianarantsoa Province, Madagascar | |
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Dimensions: | FOV: 2 cm |
Description: |
A s-face in attached smaller crystal and another one back out of focus |
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37554 Time(s) |
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Nov 29, 2016 03:16 Post subject: Re: Weird face in quartz |
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Hi Josele. May I make a suggestion to you and the administrators? There has been a number of threads about curious growth patterns and shapes in quartz. Can we not build on this thread and slightly change the topic to accommodate other contributions, as well as with links to all previous contributions? I also have a number of 'strange' forms of quartz to show.
_________________ Pierre Joubert
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Josele
Joined: 10 Apr 2012
Posts: 407
Location: Tarifa, Spain
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Posted: Nov 29, 2016 10:57 Post subject: Re: Weird face in quartz |
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Pierre, of course you can use this thread to show your weird quartz when you want. I'm already looking forward to see them!
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Nov 29, 2016 11:36 Post subject: Re: Weird face in quartz |
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Josele wrote: | Pierre, of course you can use this thread to show your weird quartz when you want. I'm already looking forward to see them! |
Fantastic! Thank you Josele. I will do so when time allows:-)
_________________ Pierre Joubert
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Cesar M. Salvan
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Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Nov 29, 2016 12:08 Post subject: Re: Weird face in quartz |
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Pierre Joubert wrote: | Hi Josele. May I make a suggestion to you and the administrators? There have been a number of threads about curious growth patterns and shapes in quartz. Can we not build on this thread and slightly change the topic to accommodate other contributions, as well as with links to all previous contributions? I also have a number of 'strange' forms of quartz to show. |
Hi Pierre!,
I take the liberty to speak as the FMF administrators team. It is a great suggestion and following the very good response from Josele, of course go ahead and publish your quartz crystals with strange shapes or difficult to explain faces. It will convert the thread in a very interesting crystal morphology lesson.
Fortunately, It is not necessary to change anything: the thread is in the right topic (minerals and mineralogy) and it can directly incorporate other specimens with similar questions. I said fortunately, because certain changes involve an overwhelming load of work for the staff's availability (who work as volunteers) and are very delicate for the structure of the forum. The title of the thread, instead, could be changed to accommodate the plurality of case studies. We'll change it once new specimens join the discussion.
I kindly ask for an effort to maintain the idea of the thread: crystals difficult to explain, as apparently strange faces, weird morphology that could be confused with different crystal systems, or confusing or unique morphological features.
To all readers, please do not convert the thread in a collection of quartz twins, as this is a different topic, or make a mess uploading all quartz groups. The idea is to keep the good level of the discussion and convert it in a good reference for the interpretation of crystal morphology.
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Nov 30, 2016 03:19 Post subject: Re: Weird face in quartz |
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Wonderful Cesar. I am looking forward to the expansion of a topic close to my heart. Thank you!
_________________ Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: Dec 07, 2016 14:33 Post subject: Re: Weird face in quartz |
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Hi Josele and other interested FMF members. Here is my first contribution, a quartz with goethite specimen, which I found about a year ago. There were a few similar specimens from this pocket, but not quite like this one. It has (to me) a very strange growth form, which could be partly the result of a broken and rehealed crystal. I find it hard to show the specimen as I would want to. Some of the smaller edges are rounded.
Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37098 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37041 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37001 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37085 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37010 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37025 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37006 Time(s) |
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Mineral: | Quartz with goethite |
Locality: | Ceres, Warmbokkeveld Valley, Ceres, Valle Warmbokkeveld, Witzenberg, Cape Winelands, Western Cape Province, South Africa | |
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Dimensions: | 35 x 28 x 23 mm |
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37121 Time(s) |
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_________________ Pierre Joubert
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Pete Richards
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Posted: Dec 08, 2016 11:15 Post subject: Re: Weird face in quartz |
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Hi Pierre,
Your specimen definitely qualifies as distorted! I think your second image is closest to being in a standard orientation. You may be right that it involves breaking and healing, but it is not clear that this occurred.
I've taken the liberty of capturing your second image and labeling it with the faces I think are present. r and z are the two rhombohedra that normally terminate quartz crystals, faces labeled m belong to the prism. There is no way to tell for sure which rhombohedron is which - I may have them labeled backwards - but it is usually assumed that the rhombohedron r has the larger faces. The hillocks on the top r face are a common growth feature and don't require breakage to explain; the irregular surface of the bottom r face (seen especially in image 4) is more suggestive of a broken and healed surface, but it appears to be in the proper orientation for an r face. Quartz does have a poor cleavage parallel to the rhombohedron which is sometimes the breakage plane when quartz breaks during growth, so it is possible for this to be a broken surface and still have the right orientation for a rhombohedron face.
The illuminated face in image 3 is a prism face, which is shown by the striations.
Attached is a cartoon that shows how your crystal relates to a more normal shape, in my interpretation.
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Pierre's image 2 with faces labeled. |
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Description: |
Transition from typical quartz morphology to Pierre's quartz's distorted morphology |
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37257 Time(s) |
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Josele
Joined: 10 Apr 2012
Posts: 407
Location: Tarifa, Spain
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Posted: Dec 08, 2016 17:33 Post subject: Re: Weird face in quartz |
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Nice piece, Pierre, very interesting. Without the help of Pete I would never arrive to determine the faces.
One rhombohedron much more developed than the other and few visible prism faces. Could it be called almost a pseudo cubic quartz crystal?
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Dec 09, 2016 01:42 Post subject: Re: Weird face in quartz |
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Pete Richards wrote: | Hi Pierre,
Your specimen definitely qualifies as distorted! I think your second image is closest to being in a standard orientation. You may be right that it involves breaking and healing, but it is not clear that this occurred.
I've taken the liberty of capturing your second image and labeling it with the faces I think are present. r and z are the two rhombohedra that normally terminate quartz crystals, faces labeled m belong to the prism. There is no way to tell for sure which rhombohedron is which - I may have them labeled backwards - but it is usually assumed that the rhombohedron r has the larger faces. The hillocks on the top r face are a common growth feature and don't require breakage to explain; the irregular surface of the bottom r face (seen especially in image 4) is more suggestive of a broken and healed surface, but it appears to be in the proper orientation for an r face. Quartz does have a poor cleavage parallel to the rhombohedron which is sometimes the breakage plane when quartz breaks during growth, so it is possible for this to be a broken surface and still have the right orientation for a rhombohedron face.
The illuminated face in image 3 is a prism face, which is shown by the striations.
Attached is a cartoon that shows how your crystal relates to a more normal shape, in my interpretation. |
Hi Pete. I really appreciate all your effort to analyze this specimen. The crystal form in your sketches is not uncommon from this area, so if there were no interferences, it probably would have ended up looking like that.
_________________ Pierre Joubert
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Pierre Joubert
Joined: 09 Mar 2012
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Location: Western Cape
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Posted: Dec 09, 2016 01:46 Post subject: Re: Weird face in quartz |
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Josele wrote: | Nice piece, Pierre, very interesting. Without the help of Pete I would never arrive to determine the faces.
One rhombohedron much more developed than the other and few visible prism faces. Could it be called almost a pseudo cubic quartz crystal? |
Hi Josele. We are blessed to have people like Pete on the forum! I realize again and again that there are many factors that can affect crystal growth in a pocket. These factors make crystal growth the interesting topic that it is.
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Pierre Joubert
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Posted: Dec 09, 2016 05:17 Post subject: Re: Weird face in quartz |
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Sorry Pete, my message should have read like this: 'The crystal forms in your first 3 sketches are not uncommon from this area, so if there were no interferences, it probably would have ended up looking like one of those.'
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Reef
Joined: 13 Dec 2016
Posts: 36
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Posted: Oct 19, 2017 15:20 Post subject: Re: Weird face in quartz |
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With your permission, I will continue to display rare quartz faces
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 20x10mm |
Description: |
face of a rhombohedron (012) |
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33244 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x12mm |
Description: |
face of a rhombohedron (012) |
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33217 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x12mm |
Description: |
face of a rhombohedron (012) |
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33217 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x12mm |
Description: |
face of a rhombohedron (012) |
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33268 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 17x16mm |
Description: |
face of a rhombohedron (012) |
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33247 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 17x16mm |
Description: |
face of a rhombohedron (012) |
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33280 Time(s) |
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Reef
Joined: 13 Dec 2016
Posts: 36
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Posted: Oct 20, 2017 09:57 Post subject: Re: Weird face in quartz |
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Sometimes a rhombohedron (012) is replaced by a ditrigonal scalenohedron. Together with {012}, on the vertex there are occasional faces from (103) to (1.0.11), down to the pinacoid (001).
Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x17mm |
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33168 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x17mm |
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33177 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Dimensions: | 23x17mm |
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33218 Time(s) |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Here, the more noticeable is the ditrigonal skalenohedron |
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Mineral: | Quartz |
Locality: | Orenburgskaya Oblast, Southern Urals, Urals Region, Russia | |
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Description: |
Here, the more noticeable is the ditrigonal skalenohedron |
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marco campos-venuti
Joined: 09 Apr 2014
Posts: 207
Location: Sevilla
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Posted: Oct 20, 2017 11:20 Post subject: Re: Weird face in quartz |
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Hi Reef, do you think these faces are originated by dissolution (etching)? They remember the "Quarzi Gommoidi" of Luigi Bombicci from Colle Palombaia, Elba Island. He refers to a finding of quartz crystals in '800 with rounded termination due to many tiny faces on the top of the crystals.
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Reef
Joined: 13 Dec 2016
Posts: 36
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Posted: Oct 20, 2017 12:34 Post subject: Re: Weird face in quartz |
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marco campos-venuti wrote: | Hi Reef, do you think these faces are originated by dissolution (etching)? They remember the "Quarzi Gommoidi" of Luigi Bombicci from Colle Palombaia, Elba Island. He refers to a finding of quartz crystals in '800 with rounded termination due to many tiny faces on the top of the crystals. |
Hi, marco campos-venuti. As far as I can tell, it's all growth faces. At this deposit quartz with inclusions of oil, lamellar structure. Basically skeletal, i.e. growth occurred rapidly and at relatively low crystallization temperatures. On some veins, there are single samples similar to dissolution, but I think this kind is due to rapid growth.
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: Nov 15, 2017 10:23 Post subject: Re: Weird face in quartz |
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Here is another specimen with an interesting face. I cannot remember ever seeing anything similar to this. I drew a yellow arrow to indicate the area of interest.
Mineral: | Quartz, variety amethyst |
Locality: | Goboboseb Mountains, Brandberg area, Erongo Region, Namibia | |
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Dimensions: | 33 x 25 x 20 mm |
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Description: |
A pencil sketch of the specimen. |
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Mineral: | Quartz, variety amethyst |
Locality: | Goboboseb Mountains, Brandberg area, Erongo Region, Namibia | |
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Dimensions: | 33 x 25 x 20 mm |
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32602 Time(s) |
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_________________ Pierre Joubert
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