noun
abrasive; abrasive material
Technical and industrial term for materials used for grinding, polishing, or cutting, such as sandpaper, grinding wheels, or polishing compounds.
この研磨材は金属の表面を滑らかにするのに使われる。
This abrasive is used to smooth metal surfaces.
研磨材の粒子が細かいほど、仕上がりがきれいになる。
The finer the abrasive particles, the cleaner the finish.
砥石 is a whetstone or grinding stone, a specific type of abrasive tool, whereas 研磨材 is a broader category including powders, papers, and other forms.
Compound of 研磨 (grinding, polishing) and 材 (material). The exact historical derivation is uncertain, but the word follows a common pattern for technical terms.