FMF - Friends of Minerals Forum, discussion and message board

[marco campos-venuti]

The world of crystals is full of oddities, but the spiral is always an attraction for any people. The spiral is not on the C axis, but at 15-20 degrees. It is clearly not casual, because the spiral is composed of 2 branches with the same pattern. They make around 2 turns in a clockwise direction. The spiral grows with the growing crystal and reaches the surface in 2 points at 2 faces of the rhombohedron. It is clearly tridimensional. The spiral is made of small crystals, most of them look like white rhombohedral dolomite (or feldspar) mixed with some positive quartz crystals, and few yellow needles of a mineral different from rutile.
I will try to upload a video or to link to it if I learn how to do it.

[marco campos-venuti]

I uploaded a video of the crystal on youtube:
https://www.youtube.com/watch?v=ybcAAWND1D0

[jimsfault]

this is so fantastic.
that would be amazing to try and photograph! (photomicrograph)

[Martin Rich]

Sorry Marco for my silly statement, but is this a petrified hurricane? :)

Martin

[Stretch]

I was asked to post my aqua with an interesting spiral top and spiral inclusion. Not sure if they are associated or not, it seems to be more than coincidental but I honestly do not know. One thing I find strange about this piece is that half way down where the spiral jettisons out, you can see where it was trying to form the termination. So I don't know if this is an etching with a healing or if the spiral formation is a growth anomaly sprouting out the top in a 2nd generation of strange growth. Certainly an interesting piece that sparks a lot of interesting thought. I would love to hear from those that know more about how this might have been formed. Or even wild proposals of how this might happen. Anything in the interest of learning about this strange one is welcomed. I hope you enjoy it as much as I do :)
Regards,
Stretch

[Elise]

Stretch - Thanks so much for adding these pictures of this extraordinary specimen to this thread (I had asked him to). I'm looking forward to any ideas members might have regarding what is happening in this specimen and how the formation at the top relates, if at all, to the inclusion. Are there any close-ups of the inclusion itself?

Best wishes,
Elise

[Duncan Miller]

Stretch - That is really an astonishing beryl specimen. Would it be possible to post a video of it on a rotating turntable?

[marco campos-venuti]

I found an other strange spiral growth. This is an aragonite specimen from an old collection, labeled as coming from Stratoni, Chalkidiki, Greece.
No idea why it is spiral shaped,
marco

[Michael Shaw]

Hi Marco,

Fascinating aragonite. I wonder if the spiral growth could be the result of the aragonite replacing a gastropod.

Michael

[marco campos-venuti]

Hi Michael,
I was thinking the same. For the size and geometry it can be a Cerithioidea (Telescopium, family Potamididae). They are amphibious gastropod molluscs that live in brackish waters and are common in the fossil record. But its spiral is sinistral, that is quite unusual for this genera.
marco

[Elise]

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)!

[Sante Celiberti]

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

[Sante Celiberti]

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

[Bob Carnein]

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.

[John S. White]

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.