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Volume 24, page 136, 1939
NOTES AND NEWS
GRATONITE - PRELIMINARY DESCRIPTION OF A NEW MINERAL FROM CERRO DE PASCO, PERU
CHARLES PALACHE, Harvard University,
and
D. JEROME FISHER, University of Chicago.
The mineral here named was sent to the Harvard Mineralogical Laboratory for
identification by Mr. Vance of Ward's Natural Science Establishment in October
1938. A little later specimens were received at Chicago by Dr. Fisher, sent by
Dr. George W. Rust of the Geological Staff at Cerro de Pasco.
Preliminary examinations at both institutions have shown that the mineral is not
jordanite as thought by Dr. Rust, from the study of its physical properties and
analysis; and that it is not identical with any known species. The following
data give its principal characteristics:
Hexagonal, rhombohedral. a: c=1:0.4428
Forms: a 11 0, m 10 0
(trigonal), c 0001, r 101,
M 40 1, e 012,
s 021 Angle c ^ r 27°04½' c
^ s 45°38'
The principal forms are the prism and the rhombohedron
s 021, which is not
selected as unit form on the basis of x-ray study of the unit cell. Twinning not
seen.
Cleavage none. H=2½. G=6.22. Color dark lead gray. Streak black.
Composition Pb9As4S15 on basis of two closely agreeing analyses, the one by the chemist of
the Cerro de Pasco Corporation, the other by F. A. Gonyer in the Harvard
Laboratory.
A more detailed description will appear shortly. The name gratonite is in honor
of L. C. Graton, Professor of Mining Geology at Harvard University. This name
has already appeared in print in the New York Times, December 28, 1938.
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