Native sulfur crystallized on aragonite with calcite microcrystals – Cozzo Disi. An impressive specimen of native sulfur on aragonite, richly covered in calcite microcrystals, originating from the historic Cozzo Disi mine (Casteltermini, Agrigento, Sicily, Italy)—one of the most renowned sites among the classic Sicilian sulfur deposits. The specimen features numerous well-developed, brilliant yellow sulfur crystals, reaching sizes of approximately 3–3.5 cm, distributed across a substantial, highly three-dimensional aragonite matrix. A particularly fascinating feature is the extensive coating of fine calcite microcrystals upon the aragonite; these create a sparkling, delicately textured surface that offers a magnificent contrast to the larger, vivid yellow sulfur crystals. Under 365 nm UV light, the aragonite exhibits fluorescence, followed by a distinct residual luminescence (phosphorescence) once the UV source is removed—adding yet another dimension to an already extraordinary specimen. The specimen has been carefully cleaned in a laboratory setting to highlight and preserve its natural crystalline surfaces. Bituminous material that originally covered parts of the specimen has been selectively removed; faint, natural traces of bitumen remain, serving as evidence of the original geological association typical of Sicilian sulfur deposits. Locality: Cozzo Disi Mine, Casteltermini, Agrigento, Sicily, Italy Minerals: Native sulfur, aragonite, and calcite Dimensions: 27 × 21 × 13 cm Weight: 5.5 kg Sulfur crystals: up to approximately 3–3.5 cm UV response: Fluorescent and phosphorescent (afterglow) under 365 nm UV light From an old collection of Sicilian minerals, assembled over the course of several decades.