Bulletin of the National Speleological Society - ISSN 0146-9517
Number 20: 25-30 - November 1958

A publication of the National Speleological Society

A Peculiar Type of Cave Gypsum
Richard V. Dietrich and John W. Murray

Abstract

Extremely fine-grained platelets (parallel to 001) of gypsum have been found to occur in Dunford Cave, Wythe County and Pig Hole Cave, Montgomery County, Virginia. X-ray patterns obtained by any method except the sphere mount method present d values equal to those of "typical" gypsum but with notable differences in intensities of many reflections - respecially noteworthy are the intensity reversals fo d = 3.08Å and d = 2.98Å. Differential thermal analyses are significantly different from those of "typical" gypsum - this may be dependent upon the inability to prepare "typical" gypsum with the same size and crystallogrphic versus shape orientation as that of the peculiar form. Optically the peculiar type has a smaller 2V than most gypsum. Solution and reprecipitation promotes conversion of the 001 platelets to gypsum with the common fightail twin habit. Associaton of these gypsum platelets with guano may indicate that the type is formed through reactions involving organisms.

Richard V. Dietrich and John W. Murray are old team mates when it comes to cave minerals. Their previous cooperation was on a paper about Brushite and Taranakite from Pig Hole Cave, Virginia. Both men are professors at Virginia Polytechnic Institute, the former in geology, the latter in chemistry. John W. Murray is also well known to speleologists as faculty advisor to the VPI Grotto of the National Speleological Society and as chairman of the Committee on Chemistry of the National Speleological Society.

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