Tumbling Sapphires

[darb]

Gidday all - Just brought a beginners tumbler from Nat Geo and kick off the process. What I would like assistance with is tumbling of Australia sapphires, I have found some information that because sapphires are so hard that we need to use Diamond grit, initially 600# 5 cts then tumble for 2-3 weeks, then rinse with final hit with 100,000 diamond grit 5cts for the same duration. Has anyone done this and what are the pros and cons
With kind regards,
Brad J

[vegasjames]

Welcome to the forum Brad.

[geoff59]

Welcome Brad.
I’ve never done anything like this before, but I’d sure like to see all of this done up, as a good tutorial. I’ll be checking back to this thread.

[ThomasT]

I would say it's faster and easier to cabochon sapphires than trying to tumble them. I cabochon style polish rubies, sapphires and emeralds and if clear enough facet them. I haven't ever tumbled any corundum species.

[jasoninsd]

Hey Brad! I don't have an answer for your questions...but I did want to say welcome to the forum from South Dakota, USA!

[Starguy]

Silicon carbide will just barely abrade corundum. You will get some rounding by impact if the corundum is big enough. Diamond grit is expensive and you may not increase the value of the sapphire enough to cover the cost. If I were trying to tumble corundum, I would keep one or two big agates in with them to add some weight and increase the impact work in the barrel. There are some large corundum crystals that would be good if you can get a couple. I’ve got some bigguns from Madagascar.

[rmf]

darb usually sapphires have mica attached to the outside since they are metamorphic. I would tumble in SiC first to get the mica off. Why would you want to tumble sapphires? If they are Gem grade you would get better results faceting them. If they are Cab grade (star sapphires) them cut them into star stones or cats eyes. If they are just pretty color then I would start with 220 SiC to get them clean the try SiC down to 400 or 600 and see if that helps you before spending $$ on diamond grit.

[ThomasT]

Another option to consider for opaque sapphires might be to do the rough grinding work and shaping on the cab wheels before 'tumbling' in something.

[darb]

Thank you all for your feedback and comments, just to clarify we have graded sapphires the ones we have designated for tumbling are low grade, but will make good gemstones for localised jewellery displays. The diamond grit was not to expensive, 600# 10 carats cost $10 AU and also the 100,000# was the same cost. The commercial mine we sourced these from in Rubyvale Queensland (Armfest Pty Lyd) also graded the Sapphires into categories( Cut 1, Cut 2, Cabface & tumble) they also advise the tumbling media being the Diamond grit and the durations of 600# for 2-3 weeks then a 24hr intermediate rinse with water and 1 drop of detergent, then onto the final polish with 100,000# for another 2-3 weeks. So let’s see how we go, will update on the process and the outcomes.

[python]

Sounds interesting. Keep us posted and some photos of the process would be greatly appreciated 😀👍

[lordsorril]

I have not used diamond grit, but, I have used Silicon Carbide on Red and Blue Corundum. 

If you are not using pieces that have been pre-shaped or are relatively solid you will find that they chip against each other instead of wearing down. A few chips are enough to eat away at the corundum pieces in tumble.  For my own amusement: I let this play out, and in the end I had one perfect sphere of corundum and everything else in the barrel was completely destroyed.   It was an expensive experiment.

Hopefully you have better luck than I did. 

[chaosdsm]

It will be interesting to see your results.... Although diamond is 3x harder than Silicon Carbide, it's also more brittle than Silicon Carbide, so it may (just a guess at this point) break down too fast in a rotary tumbler to do much smoothing on sapphires.