Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 7 August 1981:
Vol. 213. no. 4508, pp. 646 - 648
DOI: 10.1126/science.213.4508.646
Prev | Table of Contents | Next

Articles

Polycrystalline Echinoderm Calcite and Its Fracture Mechanics

PATRICIA L. O'NEILL 1

1 Department of Zoology, Duke University, Durham, North Carolina 27706

Polycrystalline calcite was revealed by scanning electron microscopy of fractured skeletal ossicles of the sea star Echinaster spinulosus (Echinodermata, Asteroidea). Whisker-like calcite crystals were observed in specimens that were loaded in stress relaxation before being fractured; rapidly broken surfaces were smooth and glassy. The crystallites were 1300 angstroms wide and at least 3600 angstroms long and were packed together in lamellae. The lamellae were wound into spirals that formed the trabecular bars. All the crystallites in an ossicle appear to be aligned in the same direction. Geometric considerations indicate that the requirement for packing the crystallites smoothly may explain the high magnesium ion concentration of echinoderm calcite.

Submitted on December 18, 1980
Revised on April 22, 1981


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Single crystal structure analysis of sea urchin spine calcites: Systematic investigations of the Ca/Mg distribution as a function of habitat of the sea urchin and the sample location in the spine.
U. MAGDANS and H. GIES (2004)
European Journal of Mineralogy 16, 261-268
   Abstract »    Full Text »    PDF »
Biological Control of Crystal Texture: A Widespread Strategy for Adapting Crystal Properties to Function.
A. Berman, J. Hanson, L. Leiserowitz, T. F. Koetzle, S. Weiner, and L. Addadi (1993)
Science 259, 776-779
   Abstract »    PDF »
Intercalation of Sea Urchin Proteins in Calcite: Study of a Crystalline Composite Material.
A. Berman, A. Berman, L. Addadi, A. Kvick, L. Leiserowitz, M. Nelson, and S. Weiner (1990)
Science 250, 664-667
   Abstract »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)