graphite pebble

例句：

1. 1.This graphite pebble is used in the production of pencils and pens.
   这种石墨石子用于生产铅笔和钢笔。
2. 2. The graphite pebble was found on the beach, and it was believed to be a natural mineral.
   在海滩上发现了这种石墨石子，人们认为它是一种天然矿物。
3. 3. The graphite pebble has been used for centuries as a tool for carving and polishing.
   这种石墨石子自古以来就被用作雕刻和抛光的工具。