Magnetite in Denticle Capping in Recent Chitons (Polyplacophora)
- Creators
- Lowenstam, Heinz A.
Abstract
Preliminary data are presented on the physical properties and the mineralogy of the material in denticle caps of chitons. The X-ray diffraction patterns of the denticle material indicate the presence of magnetite, or possibly maghemite. This is the first indication that magnetite or possibly maghemite is precipitated by a biologic agent in sea water. Hence, the origin of magnetite reported in recent and fossil marine deposits will have to be re-examined. The hardness of the denticle material (Ca. 6 on the Mohs scale) explains why chitons are effective erosional agents of rock surfaces, particularly of limestone. From the biologic point of view the possibility is considered that the magnetic properties of the denticle caps may serve as a guidance system for the so-called homing instinct of chitons.
Additional Information
Copyright © 1962, The Geological Society of America, Inc. Received October 19, 1961. A. A. Chodos made the X-ray diffraction photographs, measured the spacings of the lines, and aided in the preparation of the pattern. Particular thanks is due to Dr. J. R. Goldsmith, who examined the X-ray diffraction photographs of samples B, C, D, of Plate 1 and stated that their patterns check those of magnetite. Dr. Goldsmith furnished also the reference sample of magnetite. Dr. B. W. Kamb aided also in the interpretation of the X-ray diffraction patterns. Mrs. E. Bingham mad the spectrochemical analyses. Mr. J. H. McLean collected the chiton samples from Monterey Bay, and Mr. J. Kiger made the microscopic preparations of chiton radulae. Research was supported by grants from Shell Development Company and the Petroleum Research Fund of the Chemical Society. Addendum: A chemical analysis of a 10-mg sample by D. Maynes, completed while the manuscript was in proof, showed the presence of FeO = 20 per cent, Fe_2O_3 = 80 per cent, corresponding to 65 per cent magnetite for the sample. The inherent errors in the procedure on very small samples are such that this is the lower limit of the concentration of magnetite in the sample analyzed.Additional details
- Eprint ID
- 47810
- Resolver ID
- CaltechAUTHORS:20140801-120801007
- Shell Development Company
- American Chemical Society Petroleum Research Fund
- Created
-
2014-08-01Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Other Numbering System Name
- Caltech Division of Geological Sciences
- Other Numbering System Identifier
- 1058