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Marty
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Post subject: Cutting calcite for the first time  Posted: Tue Aug 02, 2011 7:50 am |
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Joined: Wed Feb 23, 2011 8:25 am
Posts: 28
Location: Shasta county CA
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Continued from the other thread...
I've started my next stone. A 45 carats chunk of orangy/yellow calcite. 3 hardness and three directions of perfect cleavage.
I consulted John Sinkankas' "Gem Cutting" for some wisdom on how best to do this. "Precarious at best" was the part that stuck out the most for me. I decided to call an excellent faceter I know who has been doing it since around the time I started wearing big boy pants. His response when I told him what I was up to was: "Aw f#%&...I tried cutting one years ago. Got about 3/4's of the way finished. This is everything I tried that didn't work..."
I chose a Jeff Graham design called "Bonz". So far, I've preformed the pavilion with a very worn 600 mesh sintered diamond steel lap. Then cut in the pavilion facets with a worn 1200 dyna-lap. Both steps at about 100 rpm with lots of water. I tried to go to an 8000 mesh diamond prepolish on a zinc lap. No Good. Chips kept on appearing. Now I'm on a tin/lead lap with 50/50 mix of 14,000 & 50,000 diamond. We'll see.
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bonz.jpg [ 104.22 KiB | Viewed 929 times ]
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_________________ "I wear a necklace...so I know when I'm upside down." - Mitch Hedberghttp://www.facebook.com/gemartgallery |
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JimA
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Post subject: Re: Cutting calcite for the first time Posted: Tue Aug 02, 2011 8:15 am |
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Joined: Wed Jun 22, 2011 12:10 pm
Posts: 85
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If I may recommend something? Forget the pre-polish stage - you don't need it. You are going to have to get very creative, and think of things that are "out of the box". I use an old CD with tooth polish - NOT tooth paste - polish. Tooth enamel is a 5 on the Mohs - so paste has to be less than, and polish is less than that. Picking is going to be a problem if you turn it too fast.
Good Luck!
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JEALisa
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Post subject: Cutting Calcite Play by Play Posted: Tue Aug 02, 2011 11:42 am |
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Joined: Mon Feb 14, 2011 3:42 pm
Posts: 512
Location: WA
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Thanks so much for taking the time to share the experience Marty. I truly appreciate it. Not that I take pleasure in your suffering, but it is interesting, educational and somewhat entertaining to follow along.
I love the design you have chosen, and don't think I have seen anything cut in that design before. What I am wondering is how many new curse words you have made up....
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JimA
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Post subject: Re: Cutting calcite for the first time Posted: Wed Aug 03, 2011 3:56 pm |
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Joined: Wed Jun 22, 2011 12:10 pm
Posts: 85
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Marty...did we lose you?
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JEALisa
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Post subject: Plotting the murder... Posted: Wed Aug 03, 2011 4:39 pm |
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Joined: Mon Feb 14, 2011 3:42 pm
Posts: 512
Location: WA
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of the 45 carat calcite.... or hiding the body  _________________
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JimA
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Post subject: Re: Cutting calcite for the first time Posted: Wed Aug 03, 2011 6:25 pm |
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Joined: Wed Jun 22, 2011 12:10 pm
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I bet - cutting the "soft" stuff can be very trying to say the least. Last Cuperite I did took me 3 days to cut.
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Marty
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Post subject: Re: Cutting calcite for the first time Posted: Thu Aug 04, 2011 8:04 am |
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Joined: Wed Feb 23, 2011 8:25 am
Posts: 28
Location: Shasta county CA
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I'm still with ya. It's very slow going. The stone is approximately 17 x 13 mm and chips at the facet edges with anything more than a really light touch. Hoping to have the pavilion done today.
_________________ "I wear a necklace...so I know when I'm upside down." - Mitch Hedberghttp://www.facebook.com/gemartgallery
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JimA
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Post subject: Re: Cutting calcite for the first time Posted: Thu Aug 04, 2011 11:29 am |
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Joined: Wed Jun 22, 2011 12:10 pm
Posts: 85
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Marty - I have some large pieces if worse comes to worse.
Reverse your lap when polishing to keep the facets edges - another words have the lap turn towards the facet face like you would polish a Topaz.
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Crystal Star
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Post subject: Re: Cutting calcite for the first time Posted: Thu Aug 04, 2011 2:08 pm |
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Joined: Thu Mar 31, 2011 5:57 pm
Posts: 39
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Marty, that is a fantastic looking cut diagram and I'm really looking forward to seeing how it comes out. Good luck with it!
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Marty
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Post subject: Re: Cutting calcite for the first time Posted: Fri Aug 05, 2011 11:17 am |
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Joined: Wed Feb 23, 2011 8:25 am
Posts: 28
Location: Shasta county CA
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Well, the frustration level is getting really high. Alternating between fine grinding and prepolishing for the last three days only seems to be making the stone smaller not closer to being finished. Time to set it aside and do something else. Then go back to it.
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calcitedop.JPG [ 76.35 KiB | Viewed 880 times ]
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_________________ "I wear a necklace...so I know when I'm upside down." - Mitch Hedberghttp://www.facebook.com/gemartgallery |
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