Tourmaline with Hematite — Rolled

Tourmaline with Hematite is a mineral association between Tourmaline crystals — predominantly Schorlite (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄) — and Hematite (Fe₂O₃), formed in granitic pegmatites and hydrothermal veins where both minerals precipitate from solutions rich in iron, boron and silicates. Hematite occurs as oriented inclusions, coatings or intergrowths in the tourmaline matrix, deposited during or after crystalline growth. The visual contrast between the black to brownish-black of tourmaline and the metallic gray to brownish-red of hematite results from the compositional difference between the two minerals. The mechanical rolling process progressively rounds the ends and corners of the pieces, resulting in a smoothed external profile that enhances the visual contrast between the associated minerals. Hardness: 5.5 to 7.5 on the Mohs scale (composite). Density: 3.1 to 5.3 g/cm³ (variable depending on the proportion of hematite). Crystalline system: trigonal (tourmaline and hematite). Available variations, approximate data: Size: 2 to 7 cm Unit weight: 10 to 80 g (approx.) Average: 30 pieces per kg (approx.)