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Abrasives repairing polishing crystals
  
  Index -> Conserving, Preparing and Cleaning Minerals
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Diamond




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PostPosted: Aug 18, 2018 07:31    Post subject: Abrasives repairing polishing crystals  

I have a amethyst that was chipped and I thought I would try repairing it and I started with a basic gem tutorial saying use diamonds files for shaping then move on to lapping diamond paste 6 microns then up to 0.5 . But I soon realized that this is very basic and the jump from my wet 150 grit files to 6 microns was way too big plus possibly the hard files scratch differently to the paste on my felt Dremel pads even with water used so I closed the gap and got 250 grit files from eze lap and a set of pastes starting at 40 microns which I'm told is 320 grit but first of all this does not feel like 320 more like 4000 I can't feel any grit if I rub it between my fingers which I thought might be odd possibly...

Anyway to cut it shorter what do you guys use on crystals for chips and a perfect shine as I am struggling at the moment thanks!
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John Betts




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PostPosted: Aug 18, 2018 09:24    Post subject: Re: Abrasives repairing polishing crystals  

I would not bother. The "repair" will look worse than the chip.

If you wanted to invest a lot of money you could send it to a mineral preparation specialist that will fill the chip with a matching resin. Few specimens are worthy of such a repair.

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Bob Harman




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PostPosted: Aug 18, 2018 10:15    Post subject: Re: Abrasives repairing polishing crystals  

I agree with JOHN B. Spending significant time and money to really expertly repair and enhance mineral specimens should be done only on hi end examples. "Repairs" of the type you suggest, often turn a "mineral specimen" into more of a man created decorative object like the polished quartz crystals from China. BOB
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alfredo
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PostPosted: Aug 18, 2018 10:45    Post subject: Re: Abrasives repairing polishing crystals  

I completely support John and Bob's opinion on this. Not worth the bother to repair a specimen unless we're talking about a rock with a 5-figure or more $ value.
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lluis




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PostPosted: Aug 18, 2018 10:59    Post subject: Re: Abrasives repairing polishing crystals  

Hi, all

I do not like repairs at all....
But being an amethyst, I thing you could get the help of someones (well known in minerals, for what I understood... In MR, if I am not wrong....) that "re heal" quartz, among others, amethysts...
Yes, end specimen is light in color, but aspect is impeccable, and it has not been repaired, but re-healed... (it is a question of hydrothermal re-healing; man done, not nature done....)

Anyway. do not repair it. If you wish to re-heal, thing also that it costs money and that specimen would be man treated....

Apart of that, only too add that colors are for tastes....

With best wishes

Lluís
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Diamond




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PostPosted: Aug 18, 2018 11:10    Post subject: Re: Abrasives repairing polishing crystals  

Ah ok well unfortunately I have this one started already so I will have to finish it to the best of my abilities. I do have cross transferable skills and a fair amount of tools but I've only done this type of high precision finish with intricate plastic models I've also have experience in repairing in other areas and also sculpture and some other similar stuff but I've not got my head round this one yet. Although it's looking not bad so far I need perfect of course or near as such.

One thing was I tried silicon carbide sand paper which I read has a mohs scale of 9 - 9.5 and that seemed to barely do anything compared with the diamonds files and Dremel bits. And like I say the so called 40 micron 320 grit lapping paste is no where near 320 grits in other methods. My guess is the hardness of what the grit is mounted on but that makes it very hard to guess how to cross over between methods. I'm assuming this amethyst which also has Smokey quartz is the normal 7 mohs of quartz I guess?

The resin idea I didn't think of yet thanks for that I do actually have lots of resin and colours that mix in to make any colour... I'll keep that in mind but I have already reshaped the crystal. Pity it's so hard I knew it would be lots of work but as you say maybe too much... I do actually enjoy it though a bit like meditation rubbing it down for ages. :S

Still would like to hear and suggestions if someone has them thanks.
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Diamond




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PostPosted: Aug 18, 2018 11:14    Post subject: Re: Abrasives repairing polishing crystals  

lluis wrote:
Hi, all

I do not like repairs at all....
But being an amethyst, I thing you could get the help of someones (well known in minerals, for what I understood... In MR, if I am not wrong....) that "re heal" quartz, among others, amethysts...
Yes, end specimen is light in color, but aspect is impeccable, and it has not been repaired, but re-healed... (it is a question of hydrothermal re-healing; man done, not nature done....)

Anyway. do not repair it. If you wish to re-heal, thing also that it costs money and that specimen would be man treated....

Apart of that, only too add that colors are for tastes....

With best wishes

Lluís


Ah yes I think I might have briefly come across that maybe I'll have another proper look... Thanks.
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marco campos-venuti




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PostPosted: Aug 18, 2018 17:34    Post subject: Re: Abrasives repairing polishing crystals  

Of course natural is better as for hair, nose, breast, etc. But in some cases you want to save a specimen. Because of sentiment, because it is very valuable or because it is an educational specimen. If it is not for a fraud, I would accept a restoration. In fossils this is normal.
Apart from the ethics, you have to know that lapidary art is a very difficult job. Almost every repair is possible, but you need long experience to do this. It is often supposed that cutting a stone is an easy task. Not at all! You need almost 10 years of experience to do the job you are trying to do and it is a long work of 8 to 10 steps with many different machines.
So please don't do this at home!
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Duncan Miller




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PostPosted: Aug 19, 2018 04:02    Post subject: Re: Abrasives repairing polishing crystals  

Diamond wrote:
Anyway to cut it shorter what do you guys use on crystals for chips and a perfect shine as I am struggling at the moment thanks!


Diamond - This isn't really the appropriate forum to ask a question about lapidary. I suggest you visit the discussion forum at GemologyOnline dot com, register and then search for the "Lapidary Corner: Colored Stones" thread and post your original question there. You'll be bound to receive replies from very experienced lapidarists. There are many people who repolish damaged or opaque crystal faces (mainly quartz) and some manufacturers produce equipment specifically for this purpose, so there is a market for such goods, even if not among those who collect fine mineral specimens.

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Diamond




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PostPosted: Aug 19, 2018 05:12    Post subject: Re: Abrasives repairing polishing crystals  

Duncan Miller wrote:
Diamond wrote:
Anyway to cut it shorter what do you guys use on crystals for chips and a perfect shine as I am struggling at the moment thanks!


Diamond - This isn't really the appropriate forum to ask a question about lapidary. I suggest you visit the discussion forum at GemologyOnline dot com, register and then search for the "Lapidary Corner: Colored Stones" thread and post your original question there. You'll be bound to receive replies from very experienced lapidarists. There are many people who repolish damaged or opaque crystal faces (mainly quartz) and some manufacturers produce equipment specifically for this purpose, so there is a market for such goods, even if not among those who collect fine mineral specimens.

Thanks yes I had been looking into gem cutting although mostly with the lapping machines not so useful for my situation with heard to reach parts... I'm sure someone will help though thanks!
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Travis Hetsler




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PostPosted: Aug 25, 2018 11:34    Post subject: Re: Abrasives repairing polishing crystals  

Basic guide to polishing rocks and minerals:

Use your 150# diamond files to remove the chip completely. For the next steps you *must* use successively finer mesh sizes that no more than loosely double from one to the next (IE fine out). Ex.:150#, 300#, 600#, 1200#, 3000#, etc. Unlike wood working pushing harder does not grind deeper into the stone, so you end up with visible scratches in the end if you more than double mesh sizes. All scratches from the previous step must be ground out or they will appear as white lines at the final stages. Use a loupe or other magnifier to verify after cleaning and drying the ground surface (cleaning between grinding stages also prevents contamination of successive pads with courser material).

You can order a dremel/foredom set of resin pads for smoothing as well as polishing pastes here: wwwDOTkingsleynorthDOTcom/skshop/product.php?id=97080&catID=183. These are water cooled so use a drip leg to keep the working surface of the resin pads wet (a drip leg is simply a small gauge, clear, food grade tubing found at most hardware stores; place a hose bib on one end and an adjustable stopcock in the line to supply a steady drip from above, or just use a deep sink and barely turn the faucet on to drip).

I would also order some 3000# diamond paste to pre-polish and cerium oxide powder for the final polish (the above set comes with two blank polishing pads). These pads are run dry, except the cerium which is applied as a moist paste to the felt pad, no drip leg required. I recommend cerium oxide as it leaves a finer finish on quartz than diamond (unless you fine the diamond out to 5000#, 14000#, 50,000#, 100,000#, 150,000#+).

The above guide assumes you are using a dremel or equivalent. If you are doing this by hand it is possible but be prepared to go very slowly. I hope this helps!

-travis
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Diamond




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PostPosted: Sep 05, 2018 14:23    Post subject: Re: Abrasives repairing polishing crystals  

Travis Hetsler wrote:
Basic guide to polishing rocks and minerals:

Use your 150# diamond files to remove the chip completely. For the next steps you *must* use successively finer mesh sizes that no more than loosely double from one to the next (IE fine out). Ex.:150#, 300#, 600#, 1200#, 3000#, etc. Unlike wood working pushing harder does not grind deeper into the stone, so you end up with visible scratches in the end if you more than double mesh sizes. All scratches from the previous step must be ground out or they will appear as white lines at the final stages. Use a loupe or other magnifier to verify after cleaning and drying the ground surface (cleaning between grinding stages also prevents contamination of successive pads with courser material).

You can order a dremel/foredom set of resin pads for smoothing as well as polishing pastes here: wwwDOTkingsleynorthDOTcom/skshop/product.php?id=97080&catID=183. These are water cooled so use a drip leg to keep the working surface of the resin pads wet (a drip leg is simply a small gauge, clear, food grade tubing found at most hardware stores; place a hose bib on one end and an adjustable stopcock in the line to supply a steady drip from above, or just use a deep sink and barely turn the faucet on to drip).

I would also order some 3000# diamond paste to pre-polish and cerium oxide powder for the final polish (the above set comes with two blank polishing pads). These pads are run dry, except the cerium which is applied as a moist paste to the felt pad, no drip leg required. I recommend cerium oxide as it leaves a finer finish on quartz than diamond (unless you fine the diamond out to 5000#, 14000#, 50,000#, 100,000#, 150,000#+).

The above guide assumes you are using a dremel or equivalent. If you are doing this by hand it is possible but be prepared to go very slowly. I hope this helps!

-travis



Great yes I think this is the type of stuff I'll be doing though I've got to finish up some other stuff first :( ....
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