SUANITE, A NEW MAGNESIUM BORATE MINERAL FROM HOL KOL, SUAN, NORTH KOREA

Abstract

A new mineral from the Hol Kol mine, North Korea of the composition Mg₂B₂O₅, named suanite, has been described. The mineral is found usually as fibrous aggregates associated with kotoite and other borate minerals in marble which borders the gold-and copper-bearing diopside-clinohumite skarn mass. The crystal usually elongated parallel to [010] is monoclinic with the following dimensions: a=12.10Å., b=3.12Å., c=9.36Å., β=104°20′ (Weissenberg photographs, CuKα ?? =1.54Å.). The space group C⁵_2h-P2₁/a. The unit cell contains 4[Mg₂B₂O₅]. Colourless. Hardness 51/2. Sp. gr. 2.91. Opt. properties: α=1.596, β=1.639, γ=1.670 γ α=0.074, 2V=70° (negative); r ?? v, weak; X ?? b. The chemical analysis by N. Saito and N. Kokubu follows; SiO₂ 0.60, Al₂O₃+Fe₂O₃ 0.95, MgO 46.63, CaO 5.06, B₂O₃ 40.08, CO₂ 5.01, H₂O(+) 0.90, H₂O(-) 0.23, total 99.46%. After deduction of CaCO₃ and other impurities, MgO 53.7, B₂O₃ 46.3% against the theoretical composition MgO 53.66, B₂O₃ 46.34%. The mineral is not easily affected by cold HCl. The X-ray powder diagram of the mineral is very similar to but definitely different from, that of the artificial Mg₂B₂O₅, to which it is converted when heated up to 1, 000°C..