Spherical or subspherical particle, up to 5 cm across, produced by the accretion of sedimentary material on to a mobile grain through the action of algae.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。