I bet you didn’t know that I had a rock tumbler when I was a kid. You see, I loved rocks and minerals so much that I seriously considered becoming a geologist. I spent many hours going out hiking with my dad, looking for rocks to bring home and put into my tumbler. Often, I had a good idea of how they would turn out, but sometimes the results were a beautiful surprise.
Tumbled gemstones fascinate with their smooth textures and vibrant colors. Whether you’re new to rock polishing or have been tumbling stones for years, understanding how to test and grade the quality of your tumbled gemstones is essential. With a few practical steps, you can verify your gemstones for the best quality every time.
1. Inspect the Finish
Examine the surface of your tumbled stones. A high-quality gemstone should feel smooth and uniform without rough spots, scratches, or pits. Run your fingers over the stone and tilt it under a light source. A mirror-like shine indicates a well-polished surface, which is one of the easiest ways to determine quality.
2. Check for Consistent Shape
Next, evaluate the shape of each gemstone. While symmetry isn’t always possible due to natural variations in the stones, quality gemstones tend to have evenly rounded and unbroken edges. Avoid stones with irregular chunks or flat edges, as these are caused by improper tumbling or oversight during progress checks.
3. Examine Color and Clarity
Color and clarity are important factors of gemstone grading. Vibrant, evenly distributed colors are hallmarks of higher-grade stones. Similarly, clarity means fewer inclusions, such as cracks, spots, or cloudiness. Hold your stone up to natural light to spot inconsistencies that could affect its appeal.
4. Conduct a Hardness Test
The Mohs’ scale is important for gemstone tumbling to measure a stone’s resistance to scratching, as this impacts its tumbling durability. Perform a scratch test to confirm the stone’s hardness by comparing it with a reference mineral of the same grade. Stones polished beyond their hardness limits can deteriorate quickly, while harder gems hold up better during tumbling.
5. Perform a Bounce Test for Durability
Finally, test the gem’s durability by gently dropping it onto a hard surface from a few inches above. A quality gemstone should remain intact without cracking or flaking. This test confirms that the tumbling process has strengthened the gem, leaving you with a quality product.
If you’re serious about enhancing your artisanship, focus on testing and grading the quality of your tumbled gemstones after every session. High-quality tumbled gemstones boast a smooth surface, consistent shape, vivid colors, and excellent durability. With regular practice and attention to detail, your polished stones will stand out for all the right reasons.