CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: Nice to be here
PostPosted: Fri Dec 16, 2016 4:14 am 
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Hello everybody! I'm Kalin from Bulgaria, for 2 years reading and gathering I become a passionate fan of minerals, crystals and gems and build a nice collection. Now I think to move on with my hobby and to try to work with some rough pieces that I have - mostly nice colured agate about 100 kilos and nice amethyst same amount in differnt pieces. I have a friend that can cut them on his machine and I will give a try to sand and polish them. But I want to build my own cabbing machine complete the entire rough-to-polish process, just to order the grinding wheels in different grits. So, I have a question to those who know, how many wheels I need at minimum for a good polish and which grits to choose for agate and amethyst. If I need a fine glass finish, do you recommend using cerium oxide? Anyway any advice will be appreciated wormly!
Thanks in advance
and have a nice weekend!


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 Post subject: Re: Nice to be here
PostPosted: Fri Dec 16, 2016 4:10 pm 
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Cabbing quartz and agate are very different. Agate is tougher and grinds a bit slower, but also polishes very easily. I usually start with a 180 grit hard sintered wheel for rough shaping (80 grit sintered for very rough shaping in some cases), a 280 soft Nova brand wheel to establish the dome, then a 600, 1200 and 3000 Nova, with an optional 12k or oxide on canvas flat lap for a final polish (60k in rare cases). These numbers look like chipping at the rock with a chisel in comparison to faceting but agates and some other stones are often brightly polished at 3k. Quartz is sometimes more temperamental--some of them will be at a near-final polish at 3k, others will still look a bit hazy even after 12k. I believe a bit of cerium or zirconium oxide on canvas would clear that up, I just haven't gotten around to picking it up yet since I rarely cut macrocrystalline quartz.

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 Post subject: Re: Nice to be here
PostPosted: Sat Dec 17, 2016 3:27 am 
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Thanks Stephen!
I'll give a try with this grits to see what happen... I have enough material to practise and to learn. The agate is known as Orpheus agate, it has a nice speciffic coloured pattern, and looks cool when polished well.
Anyway, thanks again and have a nice day!


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