First synthesis of the hydroxyl end-member of humite, Mg7Si3O12(OH)2

Bernd Wunder; Olaf Medenbach; Peter Daniels; Werner Schreyer

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Research Article| June 01, 1995

First synthesis of the hydroxyl end-member of humite, Mg₇Si₃O₁₂(OH)₂

Bernd Wunder;

Bernd Wunder

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

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Olaf Medenbach;

Olaf Medenbach

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

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Peter Daniels;

Peter Daniels

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

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Werner Schreyer

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

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Author and Article Information

Bernd Wunder

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Olaf Medenbach

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Peter Daniels

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Werner Schreyer

Research Group on High-Pressure Metamorphism, Institut für Mineralogie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Publisher: Mineralogical Society of America

Received: 21 Feb 1995

Accepted: 03 Apr 1995

First Online: 04 Sep 2018

Online ISSN: 1945-3027

Print ISSN: 0003-004X

Mineralogical Society of America

American Mineralogist (1995) 80 (5-6): 638–640.

Abstract

The hydroxyl end-member of humite, Mg₇Si₃O₁₂(OH)₂, was synthesized at 30 kbar and 940 °C in the system MgO-SiO₂-H₂O (MSH). Optical properties are n_x = 1.6348(10), n_y = 1.6397(10), n_z = 1.6612(10), 2V_Z = 56.1(2)°, −Δ_n = 0.026. Results of single-crystal X-ray diffraction gave a = 4.78(2), b = 10.22(3), c = 21.02(9) Å, V = 1027(7) Å³, space group = Pbnm. The morphology of the synthetic humite crystal is comparable to that of natural F-rich humite. Microprobe analyses confirmed a nearly ideal formula, Mg_6.97(3)Si_3.02(1)-O₁₂(OH)_2.00(2).