Deposit of materials (e.g. gold, diamonds, tin, or platinum) that has been concentrated by mechanical action. Placer minerals generally have high density and resistance, and therefore may concentrate during various types of weathering.
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。