Lapidary Fundamentals: All About Gemstone Tumbling

Continuing with our Lapidary Fundamentals series, today we're sharing one of the easiest polishing techniques: gemstone tumbling. To polish a gemstone, you'll need a gemstone tumbler, but little else! In this guide, you'll learn the fundamentals of polishing gemstones, and just how easy it is to get started. The first order of business? A simple overview of gemstone tumbling for beginners.

What is Gemstone Tumbling?

Unlike gemstone faceting, which involves making cuts into a rough specimen, tumbling is the process of smoothing and polishing rocks and minerals into round, bright gemstones. To achieve this smooth finish requires placing gems into a tumbling machine, or rock tumbler. The result is a smooth, polished and soft gemstone exhibiting beautiful, organic lines and features of the specimen. Tumbled gems make popular arts and crafts items, jewelry pieces, collectibles, and decorations and come in a variety of gem species. Some of the most popular tumbled gems are agate, jasper, quartz, eye agate, obsidian glass, and organic granite rocks and wood.

The exciting thing about gemstone tumbling is that it's the most straightforward lapidary technique to learn. All you need in your studio is a gem tumbler machine, some abrasives for shaping, and the rough specimens you plan to tumble. From there, you can familiarize yourself with your device by reading the instructions, taking the proper measurements, and jumping right in. While gemstone tumbling remains one of the simplest and most accessible means of shaping gems, there are important variables to consider to optimize the end product. Ready to start tumbling?

How To Get Started

The primary materials you will work with are uncut, unpolished rocks and stones, and a tumbler machine. As such, you'll need to decide on the desired stone size before choosing a tumbler machine.

Start with Stone Size

When you tumble stones in a rock tumbler, you hand select a variety of uncut specimens to revolve in the tumbler barrel together. This enables the stones to run evenly against the abrasives, as well as one another. Sounds simple enough, right? Well, you don't want to throw a bunch of random rocks into the barrel and call it good. Instead, choose a collection of various sized stones. A solid mix includes a stone that's no bigger than half the barrel, rocks that are 1/10th the size of that large stone, and a variety of sizes in between.

Choose A Tumbler Size

Once you've decided on the size of your desired stones, buy a tumbler machine that has a barrel diameter that's double the size of your largest stone. Think of it this way: If you want to tumble a rock that's one-inch long, buy a barrel that is at least two inches in diameter. That's a small size, but it gives you the stone-to-barrel ratio for tumbling.

How Hard is the Gemstone?

You'll need to ensure that all of the gems in the barrel are the same hardness level. Hardness is a classic fundamental of gemstone faceting, as harder stones will scratch and tarnish softer stones. If you are unsure of the hardness of the gemstones you are working with, use the Mohs Hardness Scale as a cheat sheet. Of course, you can use soft filler stones to place in the batch, because these are not the product, rather an aid in polishing the gemstones.

Choosing a Gemstone Tumbling Machine

A rock tumbler is a machine that contains a turning barrel with an attached abrasive to tumble the rock. The tumbler uses a rotary mechanism to turn the stones inside the barrel. Over time, the abrasive grit smooths out the sharp edges of the stone. The result is a rounded, smooth, and polished gemstone. There are two steps to produce a tumbled gem:

1. A small grain of silicon carbide smooths the rock's surface
2. A tiny aluminum oxide abrasive polishes the smoothed rock into a bright final product

While this process is relatively straightforward, it can take weeks to achieve the final product. This technique proves that good things come to those who wait! Are polished gemstones in your future? Whether you are a hobbyist or professional Lapidary, choosing a rock tumbler can result in poorly shaped stones or perfectly polished gems.

Rotary tumblers are the most popular type of gem polishing machines, but there is another class: vibratory tumblers. Instead of rolling gemstones in a barrel, vibratory tumblers quickly shake the gems to smooth and polish them. Unfortunately, saving time with a vibratory tumbler can lead to a broken barrel. If you plan to buy a vibratory tumbler, best to save for two in case one of them calls it quits.

The Best Location To Place the Tumbler

We're going to share a secret about gemstone tumblers: they are loud. Ok, it's not exactly a secret, primarily since the noise they make isn't peaceful. The fact is that tumbling machines run non-stop for hours and weeks, and they aren't quiet in their business. That's why it's crucial to choose a strategic location for your rock tumbler. The ideal situation is to place the tumbler away from the common areas of your home or neighbors. Basements and garages are excellent choices; however, if you don't have either of these, you can build a noise-canceling box to place around your tumbler.

Tips for Gemstone Tumbling

The best thing you can do is follow the instructions of the rock tumbler you've purchased. Each machine is unique from the next, and the manufacturer's guidelines will produce the best final product. In general, these are the steps you'll take:

1. Fill the barrel with stones of equal hardness and mixed size
2. Add water to the stones
3. Add silicon carbide abrasives and tumble for 1-2 weeks, depending on the size
4. Inspect the rocks every day to monitor progress and minimize buildup
5. Wash stones outside and away from household pipes which tumbler waste can clog
6. Once all angles and edges are smooth, rinse them in a colander
7. Place stones in the barrel and add water. Use a softer abrasive to polish the gems again.

And that's all you need to be on your way! You'll have a gorgeous collection of tumbled gemstones in no time. Happy tumbling!

SHOP FOR ROUGH GEMSTONES TO TUMBLE

Agate Rough

Amethyst Rough

Citrine Rough

Jasper Rough