Biomineral Single Crystals (image) American Association for the Advancement of Science Share Print E-Mail Caption These are biomineral crystals found in a sea urchin tooth. Geologic or synthetic mineral crystals usually have flat faces and sharp edges, whereas biomineral crystals can have strikingly uncommon forms that have evolved to enhance function. The image here was captured using environmental scanning electron microscopy and false-colored. Each color highlights a continuous single-crystal of calcite (CaCO3) made by the sea urchin Arbacia punctulata, at the forming end of one of its teeth. Together, these biomineral crystals fill space, harden the tooth, and toughen it enough to grind rock. Credit Pupa U.P.A. Gilbert and Christopher E. Killian; University of Wisconsin-Madison Usage Restrictions May be used only with permission Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.