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March 24, 2019, 01:39:14 am
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Help!! Need to Re-Polish Agate Geode Slab

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Author Topic: Help!! Need to Re-Polish Agate Geode Slab  (Read 400 times)
rockbluesguitar
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« on: December 28, 2015, 05:37:43 pm »

Hi. New to rocks!! Bought a Brazilian blue dyed Agate geode slab on Ebay under 10.00 (5.99 + 3.50 / shipping). Supposed to be polished on both sides. Found a white cutting mark and a black indentation on one side.

Told by Ebay "seller" I could "fix" this by hand sanding. Tried that, then used a drill sanding wheel to try getting the mark out. Now, there's a slightly grayish area (looking at a 45 degree angle). Shining natural daylight straight through the agate, all seems blue / fine. I'd like to get this agate polished smooth and shiny on both sides 100%. Right now, reading up on re-polishing agate.

Simple Tools: Black & Decker variable speed drill. From what I read here, the answer might be to attach / bolt a small circular piece of carpet to my rubber drill attachment wheel. Not sure what polish to use: cerium oxide? Tin oxide?

Advice / Comments welcome!! Thanks.


How To Sand And Polish A Slab Or Geode Half .... Quickly - Gemstone Forum

How to Polish Cut Rocks

How to Polish Agate by Hand - eHow

List / Explanation of Different Oxides for Polishing Rocks

Covington Buff & Polish Chart - Kingsley North


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bobby1
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« Reply #1 on: December 28, 2015, 06:48:50 pm »

The light colored mark appears to be a left over saw mark that wasn't fully sanded out of the slab. To get it removed you have to go back to the coarse sanding step and sand the whole surface down below the saw mark and then go to the finer grits, sanding and polishing, etc. Polishing on the saw mark only probably won't make it look polished but will make it more evident. I use a piece of window glass and various tumbling grits with water to "flat lap" smaller pieces when I'm making doublets and triplets but this won't work for polishing. Maybe you could use a piece of carpet on your hand drill to polish it. All of this work on the surface could result in going below the penetration depth of the blue dye and the color will be less blue.
Bob
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rockbluesguitar
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« Reply #2 on: December 29, 2015, 12:15:22 am »

The light colored mark appears to be a left over saw mark that wasn't fully sanded out of the slab. To get it removed you have to go back to the coarse sanding step and sand the whole surface down below the saw mark and then go to the finer grits, sanding and polishing, etc. Polishing on the saw mark only probably won't make it look polished but will make it more evident. I use a piece of window glass and various tumbling grits with water to "flat lap" smaller pieces when I'm making doublets and triplets but this won't work for polishing. Maybe you could use a piece of carpet on your hand drill to polish it. All of this work on the surface could result in going below the penetration depth of the blue dye and the color will be less blue.
Bob

Hi!! Thanks for the advice. You have a great two-step process of polishing agate slabs!! Right now, I'd be really glad just to get the blue rock smooth 'n shiny. I remember you use a carpeted wheel covered with Cerium Oxide paste. Any brand you'd recommend? One possible advantage of the Black & Decker drill: ability to modify pressure / speed of carpet drill attachment spinning on the rock slab. Can rest the agate slab flat on a smooth kitchen counter Formica surface.

Photo is the dyed blue agate geode slab before I hand sanded it. The white cut / mark was not the end of the world. Thought a little hand sanding might take it out. Live and learn!! Should have left it alone. Famous words. With the guidance / help / knowledge here, I believe this rock might be made "new" - smooth / shiny - again!! Thanks.


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bobby1
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« Reply #3 on: December 29, 2015, 09:25:36 am »

I use carpet scraps for my wheels. You probably can get it from your local carpet store. It is an office carpet that is 1/4" thick, probably nylon or some such material. Cut out a disk and glue it to one of those rubber disk attachments.
Bob
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rockbluesguitar
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« Reply #4 on: January 01, 2016, 03:15:08 pm »

What about polishing paste?
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bobby1
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« Reply #5 on: January 01, 2016, 04:43:27 pm »

Generally cerium oxide is used to polish agate.
Bob
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