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Smelt Quartz?

Posted by Kristi Hugs  
Re: Smelt Quartz?
July 16, 2012 03:58PM
These have been about for a few years now, a friend of mine in Holland bought some made into a beaded necklace, but didn't know that they were fake, but then again she isn't a gemmologist or mineral colloctor, she took them back to the shop and got her money back, after I pointed out to the dealer that they were fake.
Re: Smelt Quartz?
July 16, 2012 06:31PM
Here's a photo of smelt quartz
Attachments:
open | download - IMG_9033.JPG (29.1 KB)
Re: Smelt Quartz?
July 16, 2012 10:29PM
    
To answer an earlier comment, the ripples and so on are not caused by the fluidity of glass. This has been pretty extensively disproven. Think of precision telescope mirrors and the tolerances to which they are ground, and what effect the distortion would have over time. Rather, the thicker bottom is related to the method of production. Instead of the aforementioned float process on Sn, glass had to be blown or treated similarly to form windows. I think there's an article about it on Wikipedia somewhere.
Re: Smelt Quartz?
July 17, 2012 01:30AM
Evan,

I was planning to make that point.

My 60 year old windows show no ripples or other distortions. Perfect from top to bottom.

Colored "art glass" and some "stained" glass are designed to show ripples. The pigments are a horror story of toxic metals.

I have some interesting books about what is termed "pressed glass".

It is an old technique, but is still used today to simulate ornate crystal, though it fools no one..

A carefully formed mold is filled with molten soda glass, sometimes pigmented and then a plunger is driven into the mold.

The shapes produced are very beautiful and can be incredibly intricate. Moslty for goblets and such.

My favorite is "Sandwich Glass" by Ruth Webb Lee. All about the Boston and Sandwich Glass Company of Sandwich Village near Boston..

Don't know if the name Sandwich Glass relates to the food item, but the process is surely sandwich like.

If anyone has any broken fragments of early Roman Glass to donate to me, I would love to get some X-Ray spectra from them.

Bart
avatar Re: Smelt Quartz?
July 17, 2012 02:40AM
Bart,

Make sure that the proper provenance is provided before you accept them!grinning smiley

Cheers!

Steve
Re: Smelt Quartz?
July 17, 2012 04:07AM
    
I guess I should do a little research before I discuss "old facts" from my science education 40 - 50 years ago. I stand humbly corrected and am stilll willing to learn.
Re: Smelt Quartz?
July 17, 2012 05:53AM
Steve R.

Art and antiquities authentication was one of the directions I once favored as a direction for my business. It's part of the reason I have a huge library. Thinking I needed to know something about everything, and that book space was more important than living space.

It turns out that it is a starvation business practice. People come to you to confirm their treasures AFTER they buy them so my job became giving them the bad news.

I still like books more than Google.

Bart
Re: Smelt Quartz?
July 18, 2012 10:13AM
hi , we often talk about looking for bubbles into the pieces to help identify glass material . but i think it's can difficult for newcomers to make the difference between enhydro in a real quartz point and bubbles in fakes glass made look alike quartz points .I think we must explain the difference cause im think than many real quartz points with enhydros will be trash away.
avatar Re: Smelt Quartz?
July 18, 2012 01:01PM
Has anyone ever seen a really round bubble in quartz? I never have. I mean the shape of the cavity not any bubble moving around inside it.?

Rock Currier
Crystals not pistols.
Re: Smelt Quartz?
July 18, 2012 01:29PM
Has anyone ever seen liquid-filled bubbles in glass? Liquid inside the "bubble" would seem to indicate hydrothermal origin rather than a melt, as in glass.
'
avatar Re: Smelt Quartz?
July 18, 2012 07:41PM
I think I smelt someone here pulling my leg.

Rock Currier
Crystals not pistols.
Re: Smelt Quartz?
July 19, 2012 12:26AM
yes cause us we know what we talking about but it's not the case for everyone .the proof my sister really believe a long time than the quartz from herkimer i give her was fakes ones cause of the air bubble in the enhydro.im telling her to check if she seen bubbles in the pieces she buy to find the difference with glass.the first quartz points she bought in his life look all like the kind of thing we seen in this topic.the guy who's open this topic dont even know where to find simple real quartz point .how we can know he dont make the same idiot mistake .we receive help request for id of simple clear quartz point each month on this website.i dont think this kind of members known a simple thing about minerals .if we dont explained them well the will never learn. it's why i made this message. I kwow it's bring nothing new to many of us.
avatar Re: Smelt Quartz?
July 20, 2012 12:46AM
Evan Johnson (2) Wrote:
-------------------------------------------------------
> To answer an earlier comment, the ripples and so
> on are not caused by the fluidity of glass. This
> has been pretty extensively disproven. Think of
> precision telescope mirrors and the tolerances to
> which they are ground, and what effect the
> distortion would have over time. Rather, the
> thicker bottom is related to the method of
> production. Instead of the aforementioned float
> process on Sn, glass had to be blown or treated
> similarly to form windows. I think there's an
> article about it on Wikipedia somewhere.

It may depend on the composition (and age?) of the glass.

In the UK, I have seen large Carolean glass window panes in their original frames and where, over the course of 350 years, the glass had 'flowed' so that when, viewed from outside at a suitable angle, it seems to hang, almost like cloth, in swags.There is no way that effect could have been created in manufacture (IMHO).
Re: Smelt Quartz?
July 20, 2012 09:10AM
    
Having found the original Wikipedia link I referenced, I post the subheading here:
[en.wikipedia.org]
One can follow the references and agree, or not. Of course, I can't speak to what you observed, and I guess it's conceivably possible that a MUCH lower-melting glass was used, and was therefore fluid over long time scales. However, I still suspect it is a manufacturing issue.
Regards,
EMJ
avatar Re: Smelt Quartz?
July 20, 2012 01:54PM
Thanks. That was an interesting link. It may be that 'flow' is the wrong explanation. Imagine that a large, heavy but relatively thin sheet of glass is suspended in a slightly loose fitting frame that does not firmly clamp the glass to the frame. The result would be that the entire weight of the pane of rests on the small surface area of the bottom edge with a relatively large downward force per unit of area. Now, if glass truly flowed, however slowly then, over a long period, the glass would flow into any crack, hole or unevenness in the bottom of the frame, the bearing surface. But no one has (AFAIK) either seen such a phenomenon nor claimed that such should occur. So we need to look for some other explanation (leaving on the side for now the assertion that 'it must be set in the manufacturing process'.

Glass behaves differently under tension and compression. Also, some behaviour varies non-linearly with the thickness of a sample. Under tension, glass exhibits a tensile strength similar to that of steel. Under compression, glass demonstrates the property of elasticity and has a substantial coefficient of restitution (commonly observed by dropping a ball onto a slab of the same composition). It's commonly assumed that, when the elasticity of a piece of glass is exceeded, it must instantly shatter and that, there can be no condition of permanent deformation (at NTP) as easily observed in many solids. But can there be permanent, if slight, distortion set up un glass where:

- The area of the distorted glass sheet is a very large area relative to the size of the permanent distortion.

- The pressure over area is sufficiently high and maintained uniformly over a very extended period.

- During a very extended period, the glass is not held at a constant temperature but heated and cooled in 24 hr cycles unequally on both sides of the sheet, with temperatures varying between absolute maxima and minima of -20 to +35 deg C and with temperature shift within any one 24 hour cycle being limited to no more than 30 deg C.

That under such circumstances a small amount permanent distortion might occur does seem as likely as the *assumption* that 'swagging' in some large antique glass sheets must be caused in the manufacturing process and not developed subsequently 'in situ'. That some permanent shape distortion can develop in almost all solids is generally well known. The point of interest is the extent to which it could be shown to exist in antique window glass within the environmental parameters loosely set out here.



Edited 1 time(s). Last edit at 07/20/2012 02:05PM by Owen Lewis (2).
avatar Re: Smelt Quartz?
July 22, 2012 05:59PM
    
Owen you make a very good argument for the flow lines and ripples to be the result of manufacturing!!!
avatar Re: Smelt Quartz?
July 22, 2012 10:04PM
Not really. We all know, roughly, the flow property of glass above a certain temperature (approaching red heat). And there is no doubt that gross thickness variations used to occur in the manufacture of window glass as a matter of course. What I was trying to convey it that might be possible for some permanent distortion to occur where the pane is constantly in a state of some considerable internal stress from its own weight (in the case of very large panes and exposed 24 hour cycles of heating and cooling with a temperature change of up to about 50 deg C and repeated throughout more than three centuries.

Whatever, it seems to be very unlikely that a 'swagging' effect could be caused in manufacture - it only because is would be quite common if it was. I don't think it is common; I have seen it only a couple of times in my life and on both occasions in uncommonly large and very old panes of window glass. These in themselves are quite a rarity I think.
Lauri
Re: Smelt Quartz?
September 07, 2012 07:09PM
I just bought some blue smeltz quartz crystals on E-Bay, luckily they didn't cost much. When I got them I could see many small bubbles and wondered if they were man made or not, they looked too perfect. Well now I know. Thanks for the info I should have looked this up first. They are pretty, but made in China!
Re: Smelt Quartz?
September 09, 2012 01:39AM
hi . smelted quartz always come polish and with a too perfect shaped to be real . i found no reasons to polish quartz others than be able to easily seen the inclusions from an other minerals. never buy polished quartz except with minerals inclusions it's best way to never been scam. anyway polished quartz crystals and without matrix or inclusions doesn't have his place in a serious collection at all. let this kind of stuff to people who want to decorate their home with.bye
Rick C.
Re: Smelt Quartz?
January 18, 2013 02:24AM
And how about those Anchovie Calcites? Whoooo..........
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