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Polishing citrine and other quartzes


#1

Hi, any advice on polishing citrine and the other stones in quartz family such as amethyst? I always end up with facets covered in deep scratches. I’ve tried different polishing compounds such as diamond, cerium oxide etc…I’ve used different polishing laps as I thought my lap may have been contaminated. I went from a Batt lap to a tin/lead lap and copper lap. Nothing seems to work well.

Everything else I cut and polish goes well. It just seems to be quartzes.

Any advice?


#2

If you’re a Gem Society member, you can access faceting survey results for various gemstones, including quartz. The most popular result for quartz is a lucite lap, a cerium oxide or aluminum oxide (“alumina”) polish, and a water lubricant.


#3

Yeah I forgot about that lol

Thanks your advice worked a treat. Now I know why my teacher never cuts quartzes lol

Thanks,

Paul


#4

I’ve never found quartz to be unusually difficult with 600, 1200, 3000, then cerium. Sometimes straight from 1200 to cerium, all depends on size of facet.
The most important thing for me is to have very good light shining on the facet and being able to view the facet from differing angles. That way I can see any scratches left from the previous cut before moving to the next grade of powder. It’s amazing how many scratches can show up at the polish stage if not properly dealt with previously.
Of course if the piece of quartz has some inclusion or other imperfections you’ll never polish those out.
For me, carving dirty quartz is far more interesting than clean quartz which ends up looking like clear glass. Much more of a challenge to make the imperfections look good.


#5

Several things…first, scratching can be caused by subsurface damage from coarser laps that has not been entirely removed by finer laps. Leave enough material to be cut down by a 600 or 1200 lap if you are using something coarser. Quartz is a material that is very susceptible to subsurface damage. Same with the 600, spend some time on the prepolish lap before polishing.

Secondly, the best polish for quartz is cerium, a good grade of cerium, not a cab grade…sometimes called French cerium or facet grade cerium.

Third, if you are using a slurry of cerium and water, don’t. This is the old method and it works, but the polish comes in just as the lap dries out and starts to tug. Then if you don’t add just a little spritz of water, your slurry dries out and you get scratches. It’s also possible to use to much cerium and get it to ball up and scratch. Best advice is to use a cerium coated or impregnated lap or a cerium crayon where the cerium is in wax. The wax prevents the scratching, as does the coated or impregnated lap. Use of a lucite lap is really old news for quartz…the coated or impregnated laps or the crayon on a suitable lap work much better. There are also composite surface laps that work well for quartz. Try looking at Gearloose’s products and Marsh Howard’s Lightning Lap products. Both will have recommendations for quartz. If you are using a BATT or a lucite lap, get the crayon (such as BATTstik). Hope this is helpful. Polishing with a modern method is much easier and faster. Quartz should not be a difficult material at all. It only has that reputation because folks don’t know how to approach it.


#6

Thanks Roy. Yes I used the cerium wax stick on a batt lap. Worked well. I think one of my coarser laps is contaminated…just changed to new laps as well.

Paul


#7

I have been using lightning laps for the quartz , 1200 then right to cerium lap. The polish and cut is very nice and fast. The cerium can cut fine facets too. The laps are resin and the 1200 will not scratch and put on a fine pre polish.


#8

Cerium oxide is the best. Something else to check out is TURBOFAN LAPS, just about the easiest laps to use & all you need is water for a lube.