CORUNDUM ROCK

Product Description

Corundum is a crystalline form of aluminium oxide (Al2O3) and one of the hardest naturally occurring minerals, second only to diamond on the Mohs hardness scale. This specimen is ideal for demonstrating extreme mineral hardness in a classroom setting and for introducing students to the mineralogy behind gemstones, since gem-quality corundum is known as ruby (red, coloured by chromium) or sapphire (any other colour, most commonly blue).

Because of its hardness, corundum is also used industrially as an abrasive, and this specimen gives students a genuine, hands-on reference sample for comparing hardness across a mineral collection, from talc (hardness 1) up to corundum (hardness 9) and diamond (hardness 10).

Specimen Details

Classroom & Lab Applications

• Mohs hardness scale demonstrations and scratch-test comparisons
• Introducing the mineralogy behind ruby and sapphire gemstones
• Building a reference mineral collection spanning the hardness scale
• Crystal system and crystal habit identification exercises
• Discussing industrial uses of abrasive minerals

Care & Handling

Corundum is extremely hard and durable, so it withstands routine classroom handling well, but store it separately from softer specimens in your collection since it can scratch them on contact. Keep specimens in a labelled tray, wipe with a dry cloth if dusty, and avoid dropping on hard surfaces to prevent chipping at crystal edges.

Why Choose LabEquip

LabEquip supplies genuine rock and mineral specimens for schools, colleges and training institutes, selected for identification accuracy and classroom durability. This corundum specimen pairs well with our other Educational Rock and Minerals when building a full Mohs hardness reference set, and complements our Calcite Rock specimen for contrasting mineral hardness at opposite ends of the scale. For institutions equipping a broader earth-science lab, our Chemistry Lab Equipment range covers complementary testing tools.

Frequently Asked Questions

1. What is corundum made of?

Corundum is a crystalline form of aluminium oxide (Al2O3), one of the simplest yet hardest oxide minerals found in nature.

2. Why is corundum important in mineralogy teaching?

It sits at 9 on the Mohs hardness scale, just below diamond, making it a key reference point when teaching students how mineral hardness is measured and compared.

3. Is this specimen a ruby or sapphire?

This is a general corundum specimen rather than gem-grade ruby or sapphire. Ruby and sapphire are gem varieties of corundum coloured by trace elements, and this sample illustrates the parent mineral itself.

4. Can corundum scratch glass?

Yes. With a hardness of 9, corundum easily scratches glass (hardness around 5.5) and most other common minerals, which makes it useful for scratch-test demonstrations.

5. How is corundum used industrially?

Because of its extreme hardness, corundum is used as an abrasive in grinding and polishing applications, in addition to its role as a source of ruby and sapphire gemstones.

6. How should corundum specimens be stored?

Store corundum separately from softer minerals in your collection, since it can scratch them, and keep it in a labelled tray away from unnecessary impact.

Last Updated: September 2026