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Author Topic: Polishing Covellite Cabochons  (Read 735 times)

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JKFoam

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Polishing Covellite Cabochons
« on: February 04, 2018, 09:43:05 AM »

New to this Board but long time rockhound.

I recently acquired some covellite and cut several cabs from it.  The only problem I have had involves the polishing.  Initially I used diamond but it left a poor polish.  Then I used tin oxide with a leather disk.  This produced a much better polish but it still doesn't have that polished snap that I am looking for.  This stone has a wonderful metalic blue color that I love.  Reminds me of the electric blue color you see in glaciers but a much darker blue.

Can someone recommend a polishing solution for covellite.

This is a very soft stone but surprisingly it didn't work like a really soft material.

Jim
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rocks2dust

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Re: Polishing Covellite Cabochons
« Reply #1 on: February 04, 2018, 12:19:24 PM »

Consensus seems to be that diamond on hard leather is correct, followed by Linde-A on hard leather. A bit of Zam to finish up (or later if it oxidizes) may help a bit.
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Amethyst Rose

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Re: Polishing Covellite Cabochons
« Reply #2 on: February 06, 2018, 12:01:52 PM »

What I have used in the past was Fabuluster on hard felt.  Sand to 1200 or better, polish with Linde A on wet leather and then Fabuluster on hard felt.  The fabuluster seems to cause the surface to flow a little better than any other polish and brings up a better shine.

Good luck.  Covellite is the messiest thing I have ever cut.  Still have about 40# of Leonard Mine material to slab and work.

Bob Johannes
The Amethyst Rose

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55fossil

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Re: Polishing Covellite Cabochons
« Reply #3 on: February 06, 2018, 01:48:41 PM »

   What does your Covelite look like?  I just polished a piece that is clear like glass but has rich fire inside. It polished up super with tin oxide on leather. I will try and post a picture.  Covelite does have opaque, translucent and all grades in between.  I love this stuff. Maybe you could post a picture, please.
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Redrummd

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Re: Polishing Covellite Cabochons
« Reply #4 on: February 06, 2018, 05:25:45 PM »

Send a cab you have polished to me and I will see what I can do with it.....

Art In Stone
PO Box 195
Fox Island WA 98333

JKFoam

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Re: Polishing Covellite Cabochons
« Reply #5 on: February 07, 2018, 08:44:14 AM »

Thank you to all who responded to my question.  Your suggestions have been a big help.  I would never have thought to use a metal polish like ZAM or Fabulustre on my own.  Again, thanks for taking the time to respond.

Amethyst Rose-  You are right, Covellite is very messy to work.  I don't know which is worse, covellite or psilomelane, both bleed black but the psilomelane seemed to dull my equipment.

55fossil- I'll post a picture of my covellite as soon as I get a chance.  My material is pretty typical I think.  It is blue black opaque and fairly heavy.  No part is transparent or translucent.  I saw some pictures on GOOGLE Images that showed some transparent covellite cabs which puzzles me since covellite is copper sulfide an opaque material.  Covellite is pretty rare as a lapidary material and I have not seen very much of it.

JKFoam
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Amethyst Rose

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Re: Polishing Covellite Cabochons
« Reply #6 on: February 07, 2018, 01:28:54 PM »

there is some rare quartz from Brazil that has inclusions of Covellite but the main material is mostly from Butte Montana and Peru and is a shiny metallic blue often with associated pyrite.

I have attached a photo of a covellite cab that I did from the Leonard Mine, Butte Montana.

Bob Johannes
The AmethysT Rose
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Ryaly2dogs

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Re: Polishing Covellite Cabochons
« Reply #7 on: February 07, 2018, 08:06:54 PM »

Oh, I am liking that!  Great popping color and the metallic luster combined.
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Amethyst Rose

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Re: Polishing Covellite Cabochons
« Reply #8 on: February 08, 2018, 10:58:54 AM »

Good rough is expensive and hard to find and it is absolutely the filthiest material I have ever worked with.  If looking for rough, look at the material closely, looking for pits where the pyrite has corroded away.  The best grades will be solid with no visible pits and a brilliant blue to purple metallic color.  I have found that the pitted material is fer more fragile as the acids from the decomposing pyrite affect the covellite.  The material from Butte Montana is better quality than the material from Summitville, Colorado, Alaska, or Peru.

It is very soft, about 2-2 1/2 in hardness and requires a light touch to get a smooth surface.  I perform on 280 Nova and work down from there with a finish on Linde ! on wet leather followed by Fabuluster on a hard felt buff.

Good luck and try to stay clean

Bob Johannes
The Amethyst Rose
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