corundum

«corundum» in Mova's school dictionary: a very hard natural mineral made of aluminium oxide… — its meaning for a pupil, its sense in the lessons and examples, with 3 sentences of Mova's corpora that use it.

part of speech

noun (corundum — uncountable)

meaning for a pupil

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

sense 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.

In the corpora

• Rubies and sapphires are one mineral, corundum, and a pinch of another element decides the colour.
• Rubies and sapphires are the same mineral, corundum; red corundum is ruby, and other colours are sapphire.
• Tiny traces of other elements, such as chromium in ruby, give corundum its colour.

Trees and pragmatics

Every meaning and example of «corundum» parsed by Mova, each sentence with its dependency tree and frames.