Biogenic limestone (IMAGE) University of Colorado at Boulder Caption Wil Srubar holds a sample cube of white biogenic limestone produced by calcifying microalgae, known as coccolithophores. Credit Glenn Asakawa / CU Boulder Usage Restrictions None License Original content 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.