Natural Black Tourmaline with Metal Base — Rough

Black Tourmaline, known mineralogically as Schorlite, is a complex boron silicate with the chemical formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄. It is the most abundant variety of the tourmaline group and forms predominantly in granitic pegmatites, hydrothermal veins and boron-rich metamorphic rocks. Its black to brownish-black color results from the high concentration of iron (Fe²⁺ and Fe³⁺) in its crystalline structure. The characteristic opacity is a direct consequence of this high concentration of iron ions, which absorb practically all visible light. Hardness: 7 to 7.5 on the Mohs scale. Density: 3.1 to 3.2 g/cm³. Crystalline system: trigonal. The product is sold with a metal base included, ready for display. The measurements and weight stated refer to the complete product (crystal + base). Available variations, approximate data: Weight: 0.150 to 0.700 kg (approx.) Dimensions: 8x4x4 cm to 14x6x6 cm (approx.)