Those stones may have been used by Neandertals as abrasive tools.
这些浮石可能被尼安德特人制造成研磨工具。
英语百科
Diamond tool
(重定向自Abrasive tools)
A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.