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Polishing grain?? Lapidary Advice needed:)

chictomato

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Hi there! I need to seek some lapidary advice on this:) I have some native cut stones, though rather well cut, but when view under 10x I can see this tiny lines running across the facets. It looks like marks left after polishing of the stone. Can this tiny graining be remove by a repolishing? Will it result in a loss in carat weight? Tia:)
 

Jim Rentfrow

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chictomato,

If you are just going to do a straight repolish the carat weight loss would be minimal. When I have done repolishing in the past I have lost a few hundreths of a carat on 2-3 carat stones. Basically you are finding the facets with the index gear and angles to match how it is already cut. The lines are from poor polish and are removed during the repolishing.
 

chictomato

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Jim Rentfrow said:
chictomato,

If you are just going to do a straight repolish the carat weight loss would be minimal. When I have done repolishing in the past I have lost a few hundreths of a carat on 2-3 carat stones. Basically you are finding the facets with the index gear and angles to match how it is already cut. The lines are from poor polish and are removed during the repolishing.

Thank u Jim for the helpful info!:)
 

PrecisionGem

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Most commercial cut stones are polished with very coarse polish, 8000 grit or less, since they are doing the final cutting and polish in one step. Well cut stones are polished with 50,000 to 200,000 grit polish. A big difference.

Repolishing a stone if you are doing every facet can be a real pain in the neck since you need to hunt around for each facet. Maybe just the table could be repolished?
 

chictomato

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PrecisionGem said:
Most commercial cut stones are polished with very coarse polish, 8000 grit or less, since they are doing the final cutting and polish in one step. Well cut stones are polished with 50,000 to 200,000 grit polish. A big difference.

Repolishing a stone if you are doing every facet can be a real pain in the neck since you need to hunt around for each facet. Maybe just the table could be repolished?

Hi Gene! Tks for the input:) I wouldn't know its a tough chore if you did not mention:) I shall check with my local cutter to see if he is willing to repolish the entire stone.
 

PrecisionGem

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But make sure your local cutter is using a fine polish, or you will be right back in the same boat. Tell him you want at least a 50,000 grit polish.
 

chictomato

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PrecisionGem said:
But make sure your local cutter is using a fine polish, or you will be right back in the same boat. Tell him you want at least a 50,000 grit polish.

Hi Gene! Tks for the kind reminder ;))
 

chrono

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CT,
Does it really matter if it is difficult to see even under 10x loupe? No, you will not lose a lot of carat weight (maybe 0.1 ct or thereabouts depending on how much polishing is done and the original size of the stone). Also, I wonder how much it will affect the overall appearance to the naked eye after it is done. Will it be noticeable or barely noticeable?
 

PrecisionGem

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Side by side, the difference between 100,000 grit polish vs 8000 grit polish is quite noticeable to the naked eye. I see commercial cut stones that are coarser than even an 8000 grit. It's similar to comparing the finish on an Ethan Allen piece of furniture, and one from Walmart.

If the facets are being just re-polished, you basically won't loose any weight. If they are being re-cut, then you will loose some weight. There is a big difference between polishing and cutting, on this board the terms are often interchanged and used incorrectly.
 

chrono

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Gene,
What is the effect that is seen in the finer polish to the naked eye? How does it affect the performance of the stone?
 

PrecisionGem

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The finer polish gives the stone an almost wet look. You don't get this with a coarse polish. This morning I am working on a purple sapphire. With sapphires I pre-polish the facets with a 8000 grit diamond polish, then go back and finish polish with 100,000. With the naked eye, I can tell which facets have been repolished with the 100,000 grit.
 
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