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32 Newbattle Terrace
Edinburgh EH10 4RT
10th May 2002
The Editor
The Edinburgh Geologist
Dear Alan
Proustite postscript
The spring edition of The Edinburgh Geologist
was full of interesting things but I was particularly struck by Brian Jacksonís
fine photograph of a proustite crystal that adorned the front cover.
From the nineteen sixties up to the present,
there has been much research into finding new optical materials and producing
highly perfect single crystals of them. There are two principal requirements,
one for crystals suitable for the production of new lasers and the other
for optical components that allow the manipulation of light emitted from
lasers.
Proustite was identified as a useful material
by Hulme et al. in 1967 and later grown in the form of optical quality
crystals several centimetres in length. Proustite has a large range of
transparency in the infrared part of the spectrum (0.6 - 13mm) and, like
its close relative pyrargyrite, has favourable symmetry for frequency doubling
and mixing.
The application of this rare mineral to laser
optics makes me wonder how many mineralogists realise the extent to which
minerals, both common and rare, are synthesized and grown as large, high-quality
crystals for applications in modern technology, far removed from mineralogy.
The growth of corundum, quartz and ruby are long
established and generally familiar, but readers may be interested to know
about others. A comprehensive list would be extremely difficult to compile
? and would occupy an intolerable amount of space here, but a small random
selection is given below to illustrate the point. Large crystals of the
following minerals, among many others, have been grown for applications
which depend upon their individual electrical, optical or magnetic properties:
| greenockite |
CdS |
zincite |
ZnO |
| zincblende |
ZnS |
periclase |
MgO |
| chrysoberyl |
Al2BeO4 |
alexandrite |
[Al,Cr]2BeO4 |
| rutile |
TiO2 |
spinel |
MgAl2O4 |
| berlinite |
AlPO4 |
beryllia |
BeO |
| fluorspar |
CaF2 |
galena |
PbS |
| magnetite |
Fe3O4 |
diamond |
C |
In addition to naturally occurring minerals, there
are many important analogues which do not occur naturally but which find
important uses in magnetic, electronic and optical technology, prime examples
being the garnets containing no silicon, such as yttrium iron garnet and
gadolinium gallium garnet.
Yours sincerely
Peter Dryburgh
References and further reading
Bardsley, W. & Jones, O. 1968. On the crystal
growth of optical quality proustite and pyrargyrite. Journal of Crystal
Growth, Vol. 3, pp. 268-271.
Dryburgh, P.M., Cockayne, B. & Barraclough,
K.G. (editors) 1987. Advanced crystal growth, Prentice Hall, 592 p.
Gentile, A.L. & Stafsudd, O.M. 1968. Czochralski-
grown proustite and related compounds, Journal of Crystal Growth, Vol.
3, pp. 272-274.
Hulme, K.F., Jones, O., Davies, P.H. & Hobden,
H.V. 1967. Synthetic proustite: a new crystal for optical mixing, Applied
Physics Letters, Vol. 10, pp. 133-135. |
