How do I cut out a small circular piece of stone?

June 28, 2011 11:05 AM

I would like to turn a piece of raw amethyst like this into a stone like this able to be mounted on a ring. What is the best way to do this assuming I have access to most hand-held power tools as well as a heavy-duty drill press?
posted by talkingmuffin to Sports, Hobbies, & Recreation (5 answers total)

Best answer: Amethyst is quartz, which is to say it is glass. Normal tools can't cut glass; you need diamond blades and bits.

That kind of aggregate amethyst is also rather fragile. Abuse it and it will shatter. I doubt you could do anything with a normal machine shop.
posted by Chocolate Pickle at 11:08 AM on June 28, 2011 [2 favorites]

The search keyword you're looking for is "lapidary" and "gemstone cutting" - there are a number of hobbyist sites and supply shops online, and they're tied pretty closely to amateur geologists, gem and mineral clubs, and rockhounds of all stripes. Amazon sells the books and tools you need - I'd recommend getting a few books before sinking money into tools. A good intro site is Bob's Rock Shop.
posted by Slap*Happy at 11:27 AM on June 28, 2011 [2 favorites]

If it's not covered specifically in the above book and you can afford a bit of trial and error, it might be worth checking out How to Make a Telescope by Jean Texereau. I think most libraries would have it. The old way of cutting holes in thick glass mirrors was to use carborundum powder with a copper pipe in a drill press. I suppose you could try mounting it crystal side down in pitch, grind the back flat and cut from that side.
posted by bonobothegreat at 2:11 PM on June 28, 2011

Power tools would almost certainly shatter amethyst. If you live virtually anywhere there should be a lapidary club, no doubt filled with old people who will be ecstatic to see some new blood. If you join up, not only can they give you the skills, but you can usually use the equipment for me.
posted by smoke at 4:35 PM on June 28, 2011

Response by poster: Hey all, thought I'd do a quick update. I purchased a 1-inch DeWalt diamond bit and plugged it into my drill press. I submerged a piece of amethyst in a plastic tub using in enough water to cover it completely. The drill press made short work of the drilling and made perfect little amethyst cylinders for me. I drilled from both the top and the underside of the amethyst and both worked quite well.

It seems the trick with the drilling process is to periodically lift the drill bit to allow water to re-lubricate the stone and keep the bit cool.

I'll try and post some photos if I have the time.
posted by talkingmuffin at 11:14 AM on August 4, 2011