corundum
C2Formal, Technical, Scientific
Definition
Meaning
An extremely hard crystalline mineral, primarily aluminium oxide, of which varieties include sapphire and ruby.
Any of the forms of aluminium oxide, valued as an abrasive and, in its gem forms, as a precious stone.
Linguistics
Semantic Notes
While "corundum" is the mineralogical term, laypeople more commonly refer to its gem varieties (ruby, sapphire).
Dialectal Variation
British vs American Usage
Differences
No significant lexical differences. Pronunciations may differ slightly.
Connotations
Neutral, technical term in both varieties.
Frequency
Equally low frequency in specialised contexts.
Vocabulary
Collocations
Grammar
Valency Patterns
Noun + of + corundum (e.g., 'a piece of corundum')Adjective + corundum (e.g., 'transparent corundum')Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Used in industries related to abrasives, cutting tools, and gemstones.
Academic
Common in geology, mineralogy, materials science, and gemology texts.
Everyday
Very rare; laypeople would say "ruby" or "sapphire".
Technical
The precise mineral name for crystalline aluminium oxide.
Examples
By Part of Speech
adjective
British English
- The corundum-bearing rock was identified.
- They studied the corundum structure.
American English
- The corundum-rich deposit was valuable.
- It was a corundum-based abrasive.
Examples
By CEFR Level
- Rubies and sapphires are both forms of the mineral corundum.
- Corundum is one of the hardest naturally occurring substances.
- The synthetic corundum produced in the lab was indistinguishable from its natural counterpart.
- Industrial-grade corundum is crushed to manufacture high-performance abrasives.
Learning
Memory Aids
Mnemonic
CORUndum is the CORE mineral for rubies and sapphires; it's CORundum.
Conceptual Metaphor
HARDNESS IS VALUE / PURITY IS PERFECTION
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'карборунд' (carborundum/silicon carbide). The Russian 'корунд' is a direct cognate.
Common Mistakes
- Misspelling as 'corandum' or 'corundrum'.
- Using it as a general term for any abrasive.
Practice
Quiz
Which of the following is NOT a variety of corundum?
FAQ
Frequently Asked Questions
No. Ruby is the red, gem-quality variety of corundum. Corundum is the mineral species, which includes ruby, sapphire, and other colours.
Its primary uses are as an abrasive (e.g., sandpaper, grinding wheels) and as gemstones (ruby, sapphire). Synthetic corundum is also used in watch bearings and lasers.
Corundum has a hardness of 9 on the Mohs scale, making it the second hardest common natural mineral after diamond (10).
Yes. Pure corundum is colourless. Trace elements cause colour: chromium for red (ruby), iron and titanium for blue (sapphire). Colourless corundum is sometimes called 'white sapphire' in gemology.
Explore