Water in Sphere-Type Opal

J. B. Jones and E. R. Segnit
Department of Geology, University of Adelaide, Adelaide, Australia
Division of Building Research, C.S.I.R.O., Melbourne, Australia

Summary: Surface areas of ‘amorphous’-type opals measured by nitrogen-absorption techniques were not consistent either with the surface area of the spheres of about 2000 Å diameter observable by electron microscopy or with the thermal dehydration data. This apparent inconsistency can be explained in terms of a smaller particulate structure of the order of 100–200 Å shown by higher resolution electron micrographs. This structure also accounts for a marked shrinkage shown in dilatometer curves of this type of opal.

Mineralogical Magazine; September 1969 v. 37; no. 287; p. 357-361; DOI: 10.1180/minmag.1969.037.287.07
© 1969, The Mineralogical Society
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