Tumbled stone

Ready-tumbled agates and jasper in an open grinding drum

Tumbled gemstones; four of the stones were not tumbled and still have sharp edges

Tumbled stones or baroque stones are gemstones that are processed together with grinding or polishing agents ( e.g. aluminum oxide ) in a rotating drum or in vibrating vessels to process the surface.

The grinding process takes place in several steps with increasingly finer abrasives. The stones rub against each other and against the abrasive, with edges and rough surfaces being gradually ground down and polished in the final grinding step . The production time in the drum is around two to five weeks per batch, depending on the desired quality. Vibration drums (spirators) are about 2/3 faster, but they can only process smaller stones.

In contrast to other types of smooth cut such as cabochons or spheres , the shape of tumbled gemstones is left to chance, as the rough stones are neither preformed nor can it be predicted which surfaces will rub against each other during production. Each tumbled stone is therefore unique .

literature

• Jaroslav Bauer, Vladimír Bouška: Gemstone Guide . Verlag Werner Dausien, Hanau / Main 1993, ISBN 3-7684-2206-2 , p. 52-53 .
• Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th, revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 75 .

Web links

Commons : Tumble-polished stone  - collection of images, videos and audio files

• Christian Hausen: Tumbled stones. In: trommelsteine.at. May 1, 2016, accessed January 5, 2020 .