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Post by Starguy on Sept 27, 2021 14:44:04 GMT -5
I pushed a few bots through the 8” saw today. I hope to do more tomorrow. All shown dry.  |
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Post by miket on Sept 27, 2021 15:09:15 GMT -5
Looks like you got some good ones, Brent.
Very nice!
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Post by jasoninsd on Sept 27, 2021 16:15:37 GMT -5
OMG! I know EXACTLY where you got those! I should head up there tomorrow - LOL! You really picked some good ones there Brent!  |
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Post by Starguy on Sept 27, 2021 16:47:58 GMT -5
jasoninsd Hand picking them helped me get some good ones. I always get good ones through online ordering too. You’re lucky to live close. My pile of bots is a little overwhelming. I will break down a few this week.
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Post by Starguy on Sept 29, 2021 16:02:18 GMT -5
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Post by jasoninsd on Sept 29, 2021 19:40:35 GMT -5
Are some of these what you already on-hand? I don't remember the bag from TRS being that big!  A little disappointing those orbs weren't completely solid there in the middle of them... Do those containers hold just the right size for your tumbler barrel? |
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Post by Starguy on Sept 29, 2021 22:22:20 GMT -5
jasoninsdThe containers are just something to put them in after they’re sawn. I was a little disappointed by the hollow tubes in the one agate. It should still make some nice cabs though. I think I ended up with around ten pounds from TRS. Some of them I already had on hand. I sort them into rocks than can go straight to the tumbler and rocks for the saw. I already started filling one of the 12 pound barrels. I need to break more of the slabs on existing cracks. I will grind off the high spots where the saw breaks out too. Then I’ll decide on cabbing or tumbling. I didn’t saw much yesterday due to sore thumbs. Bots are lots of fun. You never know what you have until they get worked a little. Mostly they are pretty good quality. The 8” saw went through them pretty fast. I only have a couple hours into them so far. They should be fun to cab.
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Post by jasoninsd on Sept 30, 2021 18:17:41 GMT -5
I was trying to do the initial grind on a Botswana today. It's an odd shape with an inch or so of a straight edge in one spot. It's ridiculously difficult to grind that straight edge down on the flat lap. So, I took it outside and used a diamond grinding wheel attachment on my Dremel and formed it that way. Then I brought it back to the flat lap to clean it up. Worked like a charm. (Just thought I'd share that here! LOL)
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Post by Starguy on Oct 10, 2021 23:45:44 GMT -5
I was working on removing the saw break points on some of the bot slabs. I decided to pre form this one. I may have it’s brother from the same rock in the slab containers somewhere. When I find it, it would make a sweet pair of earrings.   |
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Post by Starguy on Oct 10, 2021 23:58:31 GMT -5
I was trying to do the initial grind on a Botswana today. It's an odd shape with an inch or so of a straight edge in one spot. It's ridiculously difficult to grind that straight edge down on the flat lap. So, I took it outside and used a diamond grinding wheel attachment on my Dremel and formed it that way. Then I brought it back to the flat lap to clean it up. Worked like a charm. (Just thought I'd share that here! LOL) Bots are slow to grind down. The only thing I’ve worked that is as durable or slightly more is Idaho Bruneau jasper and Montana moss agate. Believe it or not, corundum/ sapphire grinds faster than Bots or the others, at least with diamond wheels. It seems like some agates and jaspers are harder to saw too. I’m not sure why that is since there is a significant difference in hardness, (mohs 7-7.5 for agate/jasper vs mohs 9 for corundum). All that I can figure is that the crystalline structure of corundum makes it grind faster. Agate/jasper is cryptochrystaline. Whatever the difference some agates and jaspers can be extremely slow to grind. As we’ve discussed. The round cutting surface on a wheel grinder has some advantages for grind speed. The only thing I’ve ever used close to a flat grinder is a facet machine but the surfaces there are typically so small that the flat lap does it’s work pretty quick. gemfeller might be able to weigh in on this. Keep working on it I can’t wait to see your results. sincerely, Brent. |
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gemfeller
Cave Dweller 
Member since June 2011
Posts: 4,059 
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Post by gemfeller on Oct 11, 2021 1:24:42 GMT -5
I have only one thought: there's a difference between hardness and toughness in stones. I've generally found crystal aggregates like chalcedony, agate and jasper more difficult to grind than single crystal minerals (corundum xls, quartz xls etc.) And of course there are minerals like nephrite jade that have a fibrous structure making them extremely tough despite being disarmingly "soft."
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Post by jasoninsd on Oct 11, 2021 11:23:32 GMT -5
I have only one thought: there's a difference between hardness and toughness in stones. I've generally found crystal aggregates like chalcedony, agate and jasper more difficult to grind than single crystal minerals (corundum xls, quartz xls etc.) And of course there are minerals like nephrite jade that have a fibrous structure making them extremely tough despite being disarmingly "soft." That's a great way of looking at it! Thanks for chiming in. So far, I think the most difficult materials to grind (for me) are certain Prairie Agates from SD, Montana Agate, and a Flor de Durazno Lace Agate (Crazy Lace subcategory). These always take FOREVER to get a dome on a cab on the flat lap! LOL |
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Post by rockjunquie on Oct 11, 2021 11:57:11 GMT -5
The three hardest I think I've cabbed were bloodstone, MT aggie and mooka.
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Post by Starguy on Oct 11, 2021 13:39:51 GMT -5
You folks should try Bruneau jasper. Even the matrix is hard to grind. I tried to grind the matrix off some pieces so they could go in the tumbler. I gave up after what seemed like a long time. I love Bruneau and it takes an exceptional polish but it’s so hard to work. I don’t typically go beyond 14,000 diamond for a polish but with Bruneau, I see an improvement after running it on 50,000. Montana moss agate is similar. There’s nothing more satisfying than finishing a perfect scratch free dome on these materials.
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gemfeller
Cave Dweller
Member since June 2011
Posts: 4,059
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Post by gemfeller on Oct 11, 2021 18:01:37 GMT -5
Starguy I think all the so-called "porcelain jaspers" are extremely resistant to grinding. I'm referring to Bruneau, Morrisonite, Carassite and Willow Creek in particular, but Mookaite is similar. Technically I'm not sure what causes that but I've cut lots of Bruneau and Willow Creek and both give the wheels a challenge. I think some of the Nevada so-called "jaspers" from the Dead Camel Mountains formed the same way from silicfied sediments and cut similarly. Some of the Dead Camel material I've cut has been just as hard to grind as Bruneau. I'm sure there are other examples. ETA: Both Bruneau and Willow Creek formed in large thundereggs, not from silicified sediments as suggested above. Some of the Willow Creek eggs are monsters, measuring feet in diameter. Maybe 1dave can give us some insights as to why they're so hard.
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Post by Starguy on Oct 11, 2021 18:45:55 GMT -5
Thanks Rick gemfeller . I haven’t heard the term “porcelain jaspers” before. As an Idaho resident I collected Bruneau when I could find it reasonably priced. I don’t have a ton but I’ve tried to grind cab and saw some of it. Grinding is one thing. I’m retired and don’t have too much other stuff to do. Sawing Bruneau is a different matter. My 16” Covington has a very hard time with it. I think the feed speed is too high for this material. I’ve sawn some with the 16 but I need to be there constantly. It”# a true workout for the saw. Thumb pushing it through is an option but it takes a lot of time. I’m not complaining. I think this is part of the reason I love it so much. It takes such a beautiful polish. I wish I would have purchased this slab when it was available on eBay. It was too high priced for my budget, but what a beautiful piece.  |
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gemfeller
Cave Dweller
Member since June 2011
Posts: 4,059
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Post by gemfeller on Oct 11, 2021 19:24:09 GMT -5
Starguy , I think you're right about the saw feed speed on the Bruneau. My little 10-inch Lortone has a very slow feed but the only thing that's ever stopped it is Crown of Silver Psilomelane. That stuff is incredibly hard to saw! That's a beautiful slab! Stuff like that was common years ago and prices weren't too bad. But Bruneau's now commercially extinct since the government shut the mine down so it's the old supply/demand situation. Here's one I cut -- not as nice as the one you pictured but not bad either. Sorry about the reflections on the ends of the cab. I'll have to re-shoot the image one of these days. 
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Post by 1dave on Oct 11, 2021 19:45:26 GMT -5
Starguy I think all the so-called "porcelain jaspers" are extremely resistant to grinding. I'm referring to Bruneau, Morrisonite, Carassite and Willow Creek in particular, but Mookaite is similar. Technically I'm not sure what causes that but I've cut lots of Bruneau and Willow Creek and both give the wheels a challenge. I think some of the Nevada so-called "jaspers" from the Dead Camel Mountains formed the same way from silicfied sediments and cut similarly. Some of the Dead Camel material I've cut has been just as hard to grind as Bruneau. I'm sure there are other examples. ETA: Both Bruneau and Willow Creek formed in large thundereggs, not from silicified sediments as suggested above. Some of the Willow Creek eggs are monsters, measuring feet in diameter. Maybe 1dave can give us some insights as to why they're so hard. I've heard that Morrisonite is metamorphic which would account for that one being compacted. A strong possibility is that they are formed with more twisty moganite than chalcedony than most agate.
That would add jade-like toughness.  |
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