Eisco Corundum Specimen (Mineral), Approx. 1″ (3cm) – Pack of 12

This aluminum oxide has a Mohs scale hardness of 9, making it one of the hardest minerals on the planet. Corundum often grows in long, hexagonal crystals, and can sometimes be found as gemstones, particularly ruby and sapphire. This mineral specimen is fantastic for use in mineral hardness exercises, as well as lessons in differentiating between cleavage and crystal habit.