corundum

noun (corundum — uncountable)

«corundum» in the English dictionary: everyday — its meanings, how the lessons use it, and examples, each with its tree on Mova.

Everyday

Corundum is a very hard natural mineral made of aluminium oxide; rubies and sapphires are coloured kinds of corundum. tree →

In the lessons

In science lessons about rocks and minerals, corundum scores 9 on the Mohs scale of hardness, second only to diamond (10). Because it is so hard, crushed corundum is used to make sandpaper and grinding tools (emery). Red corundum is ruby; blue and other colours are sapphire.

Examples

Rubies and sapphires are both corundum. tree →
Corundum is harder than almost any other mineral. tree →
On the Mohs scale, corundum is 9 and diamond is 10. tree →
Emery boards for nails contain corundum. tree →
Pure corundum has no colour. tree →
The museum showed a big red crystal of corundum. tree →

Note

Uncountable. Pronounced «kuh-RUN-dum». A trap: ruby and sapphire are the same mineral, just different colours caused by tiny amounts of other metals.

On Mova

Trees and pragmatics of «corundum» in the school dictionary: every meaning and example parsed by Mova, with its dependency tree and frames.
«corundum» in the school dictionary on Mova free.

This page in Markdown → https://md.dictionary.elamur.ai/free/en/english/corundum/