François Ernest Mallard

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Ernest-François Mallard.

François Ernest Mallard (born February 4, 1833 in Châteauneuf-sur-Cher , † July 6, 1894 in Paris ) was a French crystallographer and mineralogist . From 1872 to 1894 he was a professor at the École nationale supérieure des mines de Paris . From 1890 he was an elected member of the Académie des sciences .

Services

Mallard became famous for his studies on twin crystals . Today the theories and descriptions of Bravais , Mallard and Friedel are known as the French School . According to the empirical rules of Mallard, the twin operation belongs to the symmetry of the crystal lattice ( holohedry ) but not to the symmetry of the crystal structure ( Meroedrie ). This form of twinning is called merohedral twins or TLS twins (from English twin-lattice symmetry ). Although Mallard found these rules long before the first X-ray diffraction experiment, they are still of great importance in crystal structure analysis today .

Mallard is also considered to be the first to describe the minerals Boleit (1891), Cumengeit (1893) and the cristobalite variety Lussatite . Together with Friedel, he determined the composition of moissanite for the first time in 1892 .

In 1888 he was accepted as a corresponding member of the Russian Academy of Sciences in Saint Petersburg .

Honors

A mineral newly discovered in the "Lucky Boy" silver mine (Utah, USA) and described by Marie Adolphe Carnot in 1879 was named mallardite in his honor .

literature

Individual evidence

  1. ↑ G. Donnay, JDH Donnay: Classification of triperiodic twins . In: Canadian Mineralogist . tape 12 , 1974, p. 422-425 ( online ).
  2. ↑ MJ Buerger: The genesis of twin crystals . In: American mineralogist . tape 30 , 1945, p. 469-482 ( HTML ).
  3. ^ H. Klapper, Th. Hahn: The application of eigensymmetries of face forms to anomalous scattering and twinning by merohedry in X-ray diffraction . In: Acta Crystallographica Section A Foundations of Crystallography . tape 66 , no. 3 , 2010, p. 327-346 , doi : 10.1107 / S0108767310001091 .
  4. ^ Foreign members of the Russian Academy of Sciences since 1724. François Ernest Mallard. Russian Academy of Sciences, accessed October 3, 2015 (Russian).
  5. ↑ John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Mallardite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 (PDF 67.6 kB)
  6. ↑ Mallardite, a new mineral from the Lucky Boy silver mine , according to Ad. Carnot, in: Correspondence sheet of the zoological-mineralogical association in Regensburg , year 35 (1881)
personal data
SURNAME Mallard, François Ernest
BRIEF DESCRIPTION French crystallographer and mineralogist
DATE OF BIRTH February 4, 1833
PLACE OF BIRTH Châteauneuf-sur-Cher
DATE OF DEATH July 6, 1894
Place of death Paris