Sanakirja.org

(mineralogy) A mixed chloride and borate of magnesium that occurs as a white to green crystalline evaporite, with the chemical formula Mg₃B₇O₁₃Cl.

Boracite – Tektoborates – Mg₃B₇O₁₃Cl – Boc – 6.GA.05 – 25.06.01.01 – Orthorhombic – Pyramidal (mm2) – (Pca2₁) – A = 8.577(6) Å, – B = 8.553(8) Å, – C = 12.09(1) Å; Z = 4 – 392.03 g/mol – Colorless, white, gray, brown, orange, yellow, pale green, dark green, blue-green, or blue; colorless in transmitted light – Crystalline, disseminated (pseudocubic) – Rarely as penetration twins – None – Irregular/uneven, conchoidal – Brittle – 7 - 7.5 – Vitreous - adamantine – White – Subtransparent to translucent – 2.95 – 2.91 - 3.10 – Biaxial (+) – Nα=1.658 - 1.662, – Nβ=1.662 - 1.667, – Nγ=1.668 - 1.673 – Δ = 0.010–0.011 – None – 82° – 0.024 (weak) – None – Very slowly soluble in H₂O; Slowly but completely soluble in HCl.