Post by geostrong on May 16, 2018 10:36:08 GMT -5
Anyone ever tumbled corundum (sapphire/ruby)? I jumped in with both feet and no experience...
Let me preface this post by saying that I am in my very first batches of tumbling; Lortone 33b and one barrel is running the stone mix I got with the tumbler. The other barrel I decided to use to 'clean up' some corundum schist I collected a while back. My thought was that the rotary action of the tumbler along with the abrasion of a coarse grit would get rid of some of this mica that is covering my corundum. I was correct to a degree....
The schist has corundum, kyanite, biotite, cordierite (as iolite), and micro rutile. I have not seen any iolite in this batch, so one factor out the window. The rutile is tiny, ~ 100 microns, and lives in pressure halos around some of the corundum. So far for this tumble: 8 days at 120 SiC, 13 days at 320 SiC. As you can see in the pictures, some of the corundum has been removed, while some still rests in the dark biotite schist. I kind of love the schist as a backdrop for the beautiful corundum (though I do not expect a great polish on it)!
Here was my 'plan.'
Tumble the host rock, sacrifice the kyanite as cushioning media and get some nicely polished corundum.
My 'new plan.'
Since the kyanite is still somewhat nice at this point in the tumble I will separate it from the corundum so that it can be in its own batch and get some possibly nice polish to it.
+Mesh in the pictures is 2mm for scale.
Cor-Ky-Cord-Schist by Thomas Strong, on Flickr
Corundum Close-up by Thomas Strong, on Flickr
Corundum Close-up by Thomas Strong, on Flickr
Cor-Ky Smalls by Thomas Strong, on Flickr
Mix pieces by Thomas Strong, on Flickr
So, a few questions at this point: *Do I take the corundum to 600 grit now, or stick with the coarse tumble a bit longer? - this will remove more of the schist.
*Should I use only aluminum oxide grits? Or, will using SiC be a slower but better finish? - I have both on hand.
*I will have very little material in the barrel once I separate the kyanite, what type of media should I use? Pea gravel, rounded jasper/agate, or use my leftover plastic Lortone pellets? - the pellets seem like they may be better able to get into the nooks and crannies of the corundum...? And, I only have one more chunk of host rock that is staying in my display.
*What would be a good recipe to get these through to a beautiful polish?
*And finally, should I add the kyanite-corundum mix pieces to my corundum batch? Or, do it by hand? - they are small but neat!
Thank you all for any help!
Let me preface this post by saying that I am in my very first batches of tumbling; Lortone 33b and one barrel is running the stone mix I got with the tumbler. The other barrel I decided to use to 'clean up' some corundum schist I collected a while back. My thought was that the rotary action of the tumbler along with the abrasion of a coarse grit would get rid of some of this mica that is covering my corundum. I was correct to a degree....
The schist has corundum, kyanite, biotite, cordierite (as iolite), and micro rutile. I have not seen any iolite in this batch, so one factor out the window. The rutile is tiny, ~ 100 microns, and lives in pressure halos around some of the corundum. So far for this tumble: 8 days at 120 SiC, 13 days at 320 SiC. As you can see in the pictures, some of the corundum has been removed, while some still rests in the dark biotite schist. I kind of love the schist as a backdrop for the beautiful corundum (though I do not expect a great polish on it)!
Here was my 'plan.'
Tumble the host rock, sacrifice the kyanite as cushioning media and get some nicely polished corundum.
My 'new plan.'
Since the kyanite is still somewhat nice at this point in the tumble I will separate it from the corundum so that it can be in its own batch and get some possibly nice polish to it.
+Mesh in the pictures is 2mm for scale.
Cor-Ky-Cord-Schist by Thomas Strong, on Flickr
Corundum Close-up by Thomas Strong, on Flickr
Corundum Close-up by Thomas Strong, on Flickr
Cor-Ky Smalls by Thomas Strong, on Flickr
Mix pieces by Thomas Strong, on Flickr
So, a few questions at this point: *Do I take the corundum to 600 grit now, or stick with the coarse tumble a bit longer? - this will remove more of the schist.
*Should I use only aluminum oxide grits? Or, will using SiC be a slower but better finish? - I have both on hand.
*I will have very little material in the barrel once I separate the kyanite, what type of media should I use? Pea gravel, rounded jasper/agate, or use my leftover plastic Lortone pellets? - the pellets seem like they may be better able to get into the nooks and crannies of the corundum...? And, I only have one more chunk of host rock that is staying in my display.
*What would be a good recipe to get these through to a beautiful polish?
*And finally, should I add the kyanite-corundum mix pieces to my corundum batch? Or, do it by hand? - they are small but neat!
Thank you all for any help!