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[sdpd] Cranswickite a new mineral named in the memory of Lachlan Cranswick

 From the Rietveld mailing list :

Subject: Cranswickite a new mineral named in the memory of Lachlan Cranswick
Date: Wed, 14 Jul 2010 14:57:06 -0400
From: Ron Peterson <peterson...@geol.queensu.ca>
To: Rietveld_l...@ill.fr

It is my honour to inform everyone that the International Mineralogical
Association has recognized a new mineral species and approved that it
be named "cranswickite".

The new mineral is named in honor of Lachlan M. D. Cranswick (1968-2010)
who, as a crystallographer and mineralogist at the NRC Canadian Neutron
Beam Centre located at Chalk River Laboratories, specialized in applying
neutron beams to the studies of materials science, structural chemistry,
magnetism and geology.  He assisted many scientists and students from
universities across Canada to apply these scientific tools to advance
their research programs.  Lachlan Cranswick was passionate about ensuring
the highest quality facilities for those scientists.

Lachlan also made a significant contribution to the application of powder
diffraction techniques by helping to develop and maintain the Collaborative
  Computational Project No. 14 in Powder and Small Molecule Single Crystal
Diffraction (CCP14) (Cranswick 2008).



Below is the abstract of the manuscript that will be submitted  to the
American Mineralogist for publication

Abstract
Cranswickite is a new mineral of composition MgSO4.4(H2O) from Calingasta,
Argentina (IMA2010-016).  Cranswickite is monoclinic, space group Cc,
a = 11.9183(3)Å, b= 5.1709(1)Å, c = 12.1888(3)Å, beta = 117.537°(2),
V=  666.1 Å3, Z =4. The mineral occurs as a soft white vein filling in a
metasedimentary rock (dcalc =1.918).The atomic structure has been
determined by direct methods and refined by Rietveld refinement of powder
diffraction data. The atomic structure consists of chains of corner-sharing
magnesium-containing octahedra and sulfate tetrahedra. All the water
molecules directly coordinate magnesium in the structure. The five strongest
lines in the powder X-ray diffraction data are [dobs in Å (I)(hkl)]:
5.259 (100) (200), 3.927 (46) (1 1 -2), 3.168 (45) (1 1 -3), 4.603 (29)
(1 1 -1), 2.570 (23) (3 1 1). Infra-red and Raman spectra are very similar
to the spectra measured from starkeyite.  Cranswickite is closely related
to starkeyite MgSO4.4(H2O) that has an atomic structure where two sulfate
tetrahedra and two magnesium octahedra share corners to form a four-membered
ring and not a chain as in cranswickite.

-- 
Professor R.C.Peterson
Chairman of Undergraduate Studies in Arts and Science
Department of Geological Sciences and Geological Engineering,
Queen's University, Kingston, Ontario, Canada
613-533-6180        fax   613-533-6592



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