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Open AccessArticle

Aurihydrargyrumite, a Natural Au6Hg5 Phase from Japan

Institute for Solid State Physics, the University of Tokyo, Kashiwa, Chiba 277-8581, Japan
Sunagawa cho, Tachikawa, Tokyo 190-0031, Japan
Ehime University Museum, Ehime University, Matsuyama, Ehime 790-8577, Japan
Author to whom correspondence should be addressed.
Minerals 2018, 8(9), 415;
Received: 28 August 2018 / Revised: 14 September 2018 / Accepted: 17 September 2018 / Published: 19 September 2018
(This article belongs to the Special Issue New Mineral Species and Their Crystal Structures)
Aurihydrargyrumite, a natural Au6Hg5 phase, was found in Iyoki, Uchiko, Ehime Prefecture, Shikoku Island, Japan. Aurihydrargyrumite with a metallic silver luster occurs as a submicron- to 2 μm-thick layer on the outermost surface of the placer gold. A prismatic face may be formed by {001} and {100} or {110}. The streak is also silver white and its Mohs hardness value is ca. 2.5. Its tenacity is ductile and malleable, and its density, as calculated based on the empirical formula and powder unit-cell data, is 16.86 g·cm−3. The empirical formula of aurihydrargyrumite, on the basis of 11 Au + Hg, is Au5.95Hg5.05. Aurihydrargyrumite is hexagonal, P63/mcm, with the lattice parameters a = 6.9960(10) Å, c = 10.154(2) Å and V = 430.40(15) Å3, which is identical with the synthetic Au6Hg5 phase. The seven strongest lines in the powder X-ray diffraction (XRD) pattern [d in Å(I/I0)(hkl)] were 2.877(29)(112), 2.434(42)(113), 2.337(100)(104), 2.234(87)(211), 1.401(39)(314), 1.301(41)(404), and 1.225(65)(217). Aurihydrargyrumite forms through the weathering of mercury-bearing placer gold by involvement of self-electrorefining. This new mineral has been approved by the IMA-CNMNC (2017-003) and it is named for its composition, being a natural amalgam of gold (Latin: aurum) and mercury (Latin: hydrargyrum). View Full-Text
Keywords: aurihydrargyrumite; Au6Hg5 phase; gold; placer; self-electrorefining; Ehime; Japan aurihydrargyrumite; Au6Hg5 phase; gold; placer; self-electrorefining; Ehime; Japan
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Nishio-Hamane, D.; Tanaka, T.; Minakawa, T. Aurihydrargyrumite, a Natural Au6Hg5 Phase from Japan. Minerals 2018, 8, 415.

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