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The Georgia Mineral Society, Inc. 4138 Steve Reynolds Boulevard Norcross, GA 30093-3059 |
Ad Hoc Tumbling Group
A Special GMS Group
for People Interested in Tumbling Rocks
The Ad Hoc Tumbling Group Meets
Third Tuesday
Every Odd Month
Many people, young and old, begin their rockhound journeys by tumbling stones. It is a great way to get into the hobby and there is so much to learn from tumbling.
The GMS Ad Hoc Tumbling Group meets every odd month via Zoom to talk about all things tumbling. If you are interested, you must be a member of GMS, and all members are encouraged to submit ideas for topics to cover.
The group also sponsors and runs an annual rock tumbling contest for novice and experienced tumblers. Winners are announced at our annual Mother's Day Weekend Rock Show.
If you have any questions about the Ad Hoc Tumbling Group, please send email to
Ad Hoc Tumbling Group Message
Date: Tuesday, May 19, 2026Time: Social Time 7:00 pm, Meeting Starts at 7:30 pm
Speaker: Tumbling Contest Winners
Topic: Winners’ Showcase
Location: Virtually via Zoom Link sent to members via email
Every third Tuesday of the odd‑numbered months—January, March, May, July, September and November—our Ad‑hoc Tumbling Group logs on to Zoom for a relaxed, two‑part session. The virtual doors swing open at 7:00 pm for a quick hello and a bit of chit‑chat, giving everyone a chance to catch up and share the latest finds. At 7:30 pm we dive into the main program: a short presentation, or a member‑led discussion on anything from new polishing techniques to finding material. Whether you’re a seasoned tumbler or just curious, you’ll find something useful and a friendly community ready to welcome you.
The lapidary arts—specifically the practice of rock tumbling—often exist at the intersection of geology, engineering, and patience. While it is easy to view tumbling as a simple mechanical process of spinning stones with abrasive grit, the reality is far more complex. It requires an intimate understanding of Mohs hardness, fracture patterns, and the chemical composition of silicate minerals. This year, the GMS Ad-hoc Tumbling Group pushed these boundaries to their limits with our 2026 Tumbling Contest. As we close the books on this year’s competition, it is important to reflect on the technical milestones achieved by our members and the pedagogical value of the upcoming Winners’ Showcase.
For the 2026 competition, I made a deliberate decision to move away from "easy-to-tumble" materials like standard quartz or agate. Instead, I selected two specimens that are notorious among professionals for their temperamental nature: South Dakota Chalcedony for the Novice division and Iolite for the Experienced division.
South Dakota Chalcedony is a cryptocrystalline variety of silica that, while beautiful, is prone to micro-fractures and "pitting" if the tumble cycle is not managed with extreme precision. For our Novice participants, this material served as an excellent lesson in the importance of initial stage-one grinding. If a novice does not remove the weathered rind properly, the subsequent stages only serve to highlight the imperfections.
The Experienced division faced an even stiffer challenge in Iolite. Known as "water sapphire," Iolite’s pleochroism and its tendency to cleave along specific planes make it a nightmare for the average hobbyist. Successfully tumbling Iolite requires a mastery of barrel load ratios and a very careful watch on grit progression. Over-grinding this material can lead to significant mass loss, while under-grinding fails to achieve the high luster finish the stone is known for. The fact that our members not only attempted this but produced "masterpieces" is a testament to the growth of the GMS community.
The purpose of the GMS Ad-hoc Tumbling Group has never been purely competitive; it is fundamentally educational. Because the winning stones represent such a drastic improvement in our collective technique, it would be a missed opportunity to keep these methodologies behind closed doors.
On May 19th at 7:00 PM, we will host a virtual Winners’ Showcase via Zoom. This event is designed to bridge the gap between "how to tumble" and "how to polish like a master." The winners will be conducting a deep-dive analysis of their process. By challenging our members with complex minerals, we have fostered a spirit of inquiry and technical excellence that is rare in hobbyist circles.
The upcoming Winners’ Showcase is an invitation to every member, from the absolute newcomer to the veteran who thinks they know it all, to come and learn. As we continue to refine our craft, we must remember that the beauty of a tumbled stone is merely a reflection of the knowledge and patience invested in the process. We look forward to seeing you there and celebrating the triumph of our fellow artisans.
Reminder to all members: Please check your email for the Zoom link. Even if you did not participate in the contest, the insights shared by our winners will be applicable to all future projects, regardless of the material used. As always if you have any questions, please send them to me.
Tim Hellinger
Co-Chair (co-chair open for volunteers)
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