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Synthetic smoky quartz?
  
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Fraxinus




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PostPosted: Apr 11, 2021 13:53    Post subject: Synthetic smoky quartz?  

Hello, Friends of Minerals!

Please confirm if I correctly identify the specimen of smoky quartz as synthetic. I never heard before that such things are produced, but after looking up this forum (particularly, this thread: https://www.mineral-forum.com/message-board/viewtopic.php?t=4243), I realized that they indeed are. Additionally, there are visually very similar (but smaller) specimens sold on ebay by Chinese supplier (although not labeled as synthetic).

Symptoms:
- No mother rock can be seen
- Crystals are quite clear, with no visible inclusion of foreign material
- Growth features on the crystal surfaces are diagonal

Thank you!



RIMG0712.JPG
 Mineral: Irradiated Synthetic Quartz
 Dimensions: 130x120x110 mm
 Description:
 Viewed:  2050 Time(s)

RIMG0712.JPG



RIMG0721.JPG
 Description:
Surface features on the crystal face
 Viewed:  2034 Time(s)

RIMG0721.JPG


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James Catmur
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PostPosted: Apr 11, 2021 13:56    Post subject: Re: Synthetic smoky quartz?  

The quartz may be genuine quartz (although lab grown quartz does exist), the smoky color may well not be genuine.
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lluis




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PostPosted: Apr 11, 2021 14:01    Post subject: Re: Synthetic smoky quartz?  

I think as James: probably natural, maybe irradiated (man created smoky quartz).
I think irradiated

With best wishes

LLuís
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Fraxinus




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PostPosted: Apr 11, 2021 15:02    Post subject: Re: Synthetic smoky quartz?  

Do you think these angled surface features result from natural etching process? Other natural quartz crystals I’ve seen all have straight “terraces” perpendicular to the edge (exactly like these shown on https://www.mineral-forum.com/message-board/download.php?id=56991 , right side).

BTW, is synthetic quartz absolutely indistinguishable from natural one, by chemical composition (I mean, trace impurities) ?
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Josele




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PostPosted: Apr 11, 2021 16:14    Post subject: Re: Synthetic smoky quartz?  

I think it is a lab grown quartz.

There are many offers of this stuff in ebay, Sellers says it is natural but...
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Fraxinus




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PostPosted: Apr 11, 2021 17:43    Post subject: Re: Synthetic smoky quartz?  

I previously found one, quite similar in appearance, but smaller (link was rejected by automatic spam filter, sorry).

All of these specimens share the same traits: It's a cluster of larger crystals with a densely packed slab of small ones at the base, and some small needles growing on the surface of large crystals. This latter trait may indicate that some secondary growth had happened after larger crystals were already formed. Surface features also look similar (I would call them V-like or X-like terraces, in contrast to H-like ones found in most natural quartz crystals).

Does anyone know if needle-thin quartz crystals occur in natural specimens? In my understanding, they are indicative of rapid growth. Under slow growth conditions, they'd probably dissolve.

It would not be too much a surprise if Chinese guys grow that stuff using some decommissioned/surplus commercial quartz growing equipment. But uncertainty still remains.

Actually, I'm a chemist, my geology knowledge is very limited, so the speculations above are all theoretical. That's why I'm here)
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Matt_Zukowski
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PostPosted: Apr 11, 2021 20:15    Post subject: Re: Synthetic smoky quartz?  

On the one hand, wouldn't it be cheaper to get a natural qtz specimen and irradiate it rather than grow it in a lab?

On the other hand, the surface texture in one of your photos does have that "scalloped" look i have seen in lab-grown specimens. Also, the smaller xtals at the base were also like the lab-grown material that i have seen at Tucson, but they could be glued on in this case.
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SteveB




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PostPosted: Apr 12, 2021 00:17    Post subject: Re: Synthetic smoky quartz?  

Yes is would be cheaper in theory to collect natural crystals, but from where? Can everybody dig up such specimens in their backyard? Geology isnt that uniform. Manufacturing in bulk is probably more affordable for most. Plus “lab grown” crystals allows for intrucing other chemicals to the mix to create new unique “rarities” and even striking examples of other mineral crystals growing on/in and through the quartz crystals.

Chemically a man made quartz crystal is identical to an earth made. Which is why they are all labelled as “natural” because technically they are. These can be bought in bulk cheaply in China much like any other product. Nice specimens should come with the mined location at least though otherwise assume its man made. A giveaway is also they rarely show photos of the matrix the crystals are attached to Which is often clearly something unnatural. Its not possible to say for certain, the scalloping on the face in your photo is odd to me, not sure what caused that.

This whole issue has been progressing for years. It started with large boulder form quartz being cut into crystal shapes for the spiritualist healing/newage markets where a “giant” crystal sells well and being a dubious practice to begin with a people would say the size of the crystal gives more healing etc. Glass ones are expensive to make but with the increasing need of manufacturer minerals for realworld uses its become cheaper and easier to grow crystals and they want to grow from solution anyway. Clarity is extra work and not essential for decorative crystal unlike the field of optics.

If its location is “China” and its a bargain (tricky here, they have started to realise the same thing they are selling for $1 will sell to mineral collects for $100s or more since we primarily want a specimen naturally formed) Its probably been grown by man somewhere. A real specimen should come with information more precise as to where it was mined, however that information is just a scrap of paper anyone could look up where quartz in mined in China and pick a location and nobody would know if it was real or not. If buying You should look at all the items they are selling, it’ll be obvious if they are a proper mineral collector/dealer, an over inflated new age peddler, or someone selling lots of cheap stuff like mobile phone covers etc that theyve bought on a chinese own online wholesaler and selling to us dumb westerners who cant read chinese anyway. India has been doing similar too with manufactured / faked goods including some minerals so I would be careful. Research what the seller is selling all up and decide for yourself if its for real. If it sounds too good to be true it probably is. You should also label your examples as possibly man made if you buy such, just to help others in future if you sell or when you die. I understand the attraction of these in your display case and I personally walk away from such bargains, There are such items available at affordable prices too that did come the ground. I have a specimen journal I keep for my collection with notes like a purchase, claimed location China, possibly man made etc. For specimens I collected myself I provide GPS co-ordinates (use google maps to get if I didnt have a gps at the time of my find). The journal is not just a catalogue but also a research guide, so as measuring tools become available to me I like to note test results so if i have doubt about the rock or mineral I build data over time ( example I have a half dozen water worn black extremely dense crystals in my collection that were amoung my fathers belongings when he died, Ive never had a clue what they were, garnets or saphires maybe but after getting quality hardness scribes I eliminated those and recently I acquired a stable Specific gravity rig and can get repeatable precise measurements to three decimal places and have identified these dense stones as cassiterite).
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Fraxinus




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PostPosted: Apr 12, 2021 04:42    Post subject: Re: Synthetic smoky quartz?  

They are not glued, as there are absolutely no gaps between the small crystals at the base and the large ones. Additionally, some of these smaller guys form "bridges", emerging from the face of one crystal an going directly into face of another.
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Fraxinus




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PostPosted: Apr 12, 2021 05:01    Post subject: Re: Synthetic smoky quartz?  

Because there are vast amounts of synthetic quartz used by electronics/telecom industry, nothing apparently prohibits using some outdated facilities equipment to grow such things. It is unclear, however, how exactly this is done, maybe larger crystals are actually natural ones, used as a starter, and the slab is grown to join them. But in my view, it's even more difficult to imagine how such things with two clearly distinct crystal sizes, and with no visible mother rock, can grow in nature.

"Scalloping" on the faces is probably an etching figure. This etching can occur in nature, but it seems to happen more often than not in synthetic specimens.
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Jordi Fabre
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PostPosted: Apr 12, 2021 07:47    Post subject: Re: Synthetic smoky quartz?  

Fraxinus wrote:

Because there are vast amounts of synthetic quartz used by electronics/telecom industry, nothing apparently prohibits using some outdated facilities equipment to grow such things. It is unclear, however, how exactly this is done, maybe larger crystals are actually natural ones, used as a starter, and the slab is grown to join them. But in my view, it's even more difficult to imagine how such things with two clearly distinct crystal sizes, and with no visible mother rock, can grow in nature.

"Scalloping" on the faces is probably an etching figure. For example, picture here:
https://crystal-information.com/wp-content/uploads/2015/09/etched-quartz-example-14.jpg.
(link normalized by FMF)
This etching can occur in nature, but it seems to happen more often than not in synthetic specimens.

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Amir Akhavan




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PostPosted: Apr 12, 2021 11:08    Post subject: Re: Synthetic smoky quartz?  

Yes, synthetic.

Needles are typical and a common byproduct in industrial crystal growth, and form on the walls of the vessels, even though the seeds and the oscillator crystals grown from them are platy.
Needle-like crystals do form in nature as well.
Most people would say slim crystals have grown faster, but if you really check the literature you will find that this depends on the substance and probably lots of other circumstances. It is a problem for the pharmaceutical industry, they want to grow crystals with a specific size and habit to control the time it takes to dissolve the drugs and consequently their uptake by a patient, and some substances get more equant when they grow faster. Crystals have several "modes of growth", and they switch between them dependng on oversaturation, temperature, chemical composition of the solution etc. You can get extreme needle crystals ("whiskers") under conditions that do not promote fast growth, because then crystals can only grow along certain defects in their structure (dislocations -> "spiral growth").
Needle-formation is favored in conditions where the dissipation of crystallization heat is required (Lechatelier's principle). Quartz grows very very slow, so this has little to do with it. Same goes for diffusion-limited processes.

About surface features: there are, among other things, etch pits and growth hillocks. On a rhombohedral face (the ones forming the tip), the etch pits are more or less asymmetric triangles that point "downwards". Growth hillocks, like the one shown on the photo Jordi has posted, may look triangular, too, and then point upwards.
Such growth hillocks are what you inspect to figure out whether the specimen is lab grown.
Until now, one tale-telling feature is the absence of horizontal striations on the prism faces. Instead they are often covered by oblique patterns (growth hillocks).
The absence of striations is caused by the way they are grown - fast-growing in an alkaline (NaOH) or fluoride solution. If you grow them in water or a NaCl solution, the crystals will develop the usual striation. Nobody does that commercially yet because the crystals grow very slow under such conditions.

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Amir C. Akhavan, Hamburg, Germany
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