Mineral: Quartz (variety chalcedony), Quartz
Locality: Barros Cassal, Rio Grande do Sul, Brazil
Dimensions: 48,8 x 38,2 mm

Description: A close up of spiral-shaped inclusion. What kind of inclusion? It looks very similar to "flakes" on polished surface of chalcedony. Might it be crystobalite (quartz after crystobalite)?

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