Treasure Hunting

I’ve been working on making some updates to the site, particularly on some of the static pages.  I’ve added a few links to the Mohs Hardness Scale chart, but there’s still a lot of work to be done there and things have been quite hectic lately.  I also started a new page to give a more in-depth look at crystal quartz polishing.  So far, I’ve just added information through about the cleaning process, but as I’m still in the process of tumbling the crystals, it will be an ongoing job for quite some time.

I’ve also been trying to figure out ways to make the layout of this site a bit better.  As there are some outside limitations to the the types of themes I can use, this is a lot easier said than done.  For now, this theme seems to work the best of the options I have, but I’m not crazy about it.  I keep exploring other alternatives, but nothing else fits right now.  Oh well!  I guess I’ll keep looking awhile longer.

I did remember to add a Widget listing the top Entrecard visitors to this site.  I was a little skeptical about Entrecard at first, but through that service, I have found a great many sites that I enjoy.  It’s also brought some very interesting people here.  For those two reasons, I definitely recommend it to anyone who hasn’t signed up yet.

A lot of the fun in polishing your own stones in a rock tumbler is going out and gathering the rocks yourself. Sometimes though, this just isn’t possible either because you don’t have the time or you can’t get to the location that has the material that you want. If you’re fortunate to have a rock shop in town, you can always go there and check out what rough tumbling material they may have in stock. Even then, they may not carry what you’re wanting, especially if you’re looking for something that’s not considered to be standard rock tumbler material.

Fortunately, there are a lot of places online where you can buy almost any type of rock tumbling material that you want. You can find anything from unusual abrasives to rare rough mineral material. The picture to the left is some spotted sodalite that I bought online from The Rock Shed along with several other varieties of crushed rock. That’s another benefit of buying the supplies online. A lot of times, if you purchase tumbling material from a local rock shop, the only choice you have is buying a mixed back of stones. I much prefer to buy the stones separately and then figure out what mixture that I want to use when loading them into the rock tumbler.

Right now, I am polishing a mixture of three types of jasper in my rock tumbler. I also bought these online from The Rock Shed, and I was really impressed with the quality. The picture above shows the three jaspers: desert jasper from Madagascar, ocean jasper from Madagascar, and picture jasper from Africa. The initial grinding cycle in the rock tumbler has just ended for this batch - I ended up having to leave them in for 11 days to complete this cycle. The rocks are already looking beautiful, so I am really looking forward to seeing how they will turn out in the end.

Another place that you can get a good deal on rough tumbling material is eBay. In fact, this is a good resource for rock tumblers as well. If you’ve been wanting to buy your own rock tumbler but were hesitant about spending the money, check out prices on used rock tumblers there. I almost would prefer to buy a rock tumbler that was slightly used than a brand new one. Sometimes it takes a couple of cycles to break a new barrel in, and it’s nice if someone has already done that work for you. Be careful though - you don’t want to get one with a barrel that has been used too frequently or is in bad shape. However, if you can find a really good deal, you can always just buy a new barrel from someplace else and still save a lot of money.

I received an email today from someone asking about the various types of grit for a rock tumbler.  The type of grit you use can make a huge difference in your final polished stones, so I thought I would write up a little more about the various choices.

First, before going into the specific choices, there are some general things about rock tumbler abrasives that are important to know.  Although the abrasives used in rock tumbling are commonly called “grit”, the term grit actually refers to the size of the grains in the abrasive.  So, just like with sandpaper, the smaller the number for the grit, the more coarse the grains.  For example, Silicon Carbide 120/220 includes grains that are between 120 and 220 grit.

When using a rock tumbler, you go through a series of cycles starting with a coarser grit and moving towards a finer grit.  A coarser grit does a heavier grinding and sanding of the stones than a finer ones.  The finest grits are reserved for the polishing stages of the rock tumbling process.

Silicon Carbide - This abrasive is a compound formed from silicon and carbon.  Although it can be found naturally, it is usually man-made.  Various grit sizes of silicon carbide are basics for any rock tumbling project.  It ranks around a 9 on the Mohs scale of hardness, so it is effective as a grinding and sanding agent on most stones.  If you’re putting corundum (rubies and sapphires) in your rock tumbler, you should check into a different substance because you want your grinding and sanding grit to have a higher hardness rating than the materials you are tumbling.  However, in general, silicon carbide does a great job on other materials.

Boron Carbide - Composed of boron and carbon, this abrasive has a hardness of about 9.3 on the Mohs scale.  It acts very similar to silicon carbide, but it is much more effective if you’re tumbling corundum.  You could certainly use it in place of silicon carbide on stones other than corundum, but you’d be spending a lot more money.  Boron carbide can cost up to 10 times more than silicon carbide.  It’s also quite a bit messier to use so I definitely recommend only using it when you absolutely need it.  In fact, if you’re new to using a rock tumbler, you might want to stay away from corundum altogether for awhile and practice on other stones that are easier to polish.

Aluminum Oxide - This compound composed of aluminum and oxygen also has a hardness of about 9 on the Mohs scale.  It is most commonly used as a pre-polish and polish because of its availability in finer grain sizes.  Although it may not be the absolute best polishing agent for all material types, aluminum oxide makes up for that by being a good all-purpose polishing grit.  If you are putting a lot of mixed loads in your rock tumbler or if you just want to purchase one general compound for polishing, this is the one you want to get.

Cerium Oxide - This abrasive is reserved as a choice for a polishing agent.  It works best on stones in the 5-7 hardness range.  It’s also a good choice if you’re polishing glass pieces in your rock tumbler.  Cerium oxide gives a beautiful polish to quartz.

Chrome Oxide - This substance is another that can be used in the polishing cycle of rock tumbling.  It’s generally reserved for softer stones with deeper colors such as jade and lapis lazuli.  

So, if you’re just starting out, what are the best choices to get for rock tumbling grit?  I would recommend getting three types of Silicon Carbide (60/90 grit, 120/220 grit, and 500 grit) for the grinding and sanding cycles, Aluminum Oxide 1000 grit for the pre-polish cycle, and Aluminum Oxide Polish for your final polishing stage.  As you practice more and want to do some additional experimentation, you can try out some of the other polishing agents.

I checked on the rocks today and decided it was time to pull them out and rinse them off. To the left is a picture of what they looked like after finishing the second cycle of about 5 days in the rock tumber with a medium grit (120/220 Silicon Carbide).

It would have been better if I had separated out some of the stones and taken pictures so that you could see how nice some of them are really looking. I was in a hurry today when I did this so I didn’t take the time. I already loaded them back in the rock tumbler with Aluminum Oxide Pre-Polish for the third cycle. I’ll make sure to take the time to photograph more samplings when I am rinsing that cycle - probably in about another five days.

I’m looking into possibly making some jewelry with some of these stones when they’re done. But I also might wait until after the next batch and pick from the best of both lots. That also means that I have to decide which ones I want to polish next.