| NOUN | substance | corundom, corundum | very hard mineral used as an abrasive |
|---|
| Meaning | Very hard mineral used as an abrasive. | |
|---|---|---|
| Synonym | corundum | |
| Narrower | alumina, aluminum oxide, aluminium oxide | Any of various forms of aluminum oxide occurring naturally as corundum |
| ruby | A transparent deep red variety of corundum | |
| sapphire | A precious transparent stone of rich blue corundum valued as a gemstone | |
| Broader | mineral | Solid homogeneous inorganic substances occurring in nature having a definite chemical composition |
| Substance of | emery | A hard grey-black mineral consisting of corundum and either hematite or magnetite |