Corundum

Definition

Corundum is a crystalline form of aluminum oxide (Al2O3) that is known for its exceptional hardness and durability. It is the second hardest naturally occurring mineral after diamond, making it an important material in various industrial applications and a significant gemstone in its ruby and sapphire varieties.

5 Must Know Facts For Your Next Test

1. Corundum is commonly used as an abrasive in industrial applications due to its hardness, making it ideal for grinding and cutting tools.
2. The presence of trace elements like chromium gives rise to the red color of rubies, while iron and titanium contribute to the blue color of sapphires.
3. Corundum crystallizes in a hexagonal system and can form large, well-formed crystals that are often found in metamorphic rocks.
4. In addition to its uses in gemstones, synthetic corundum is created for use in high-performance applications like watch crystals and cutting tools.
5. The term 'corundum' is derived from the Sanskrit word 'kuruvinda', which refers to the ruby gemstone.

Review Questions

• How does the hardness of corundum compare to other minerals, and what implications does this have for its industrial applications?
  • Corundum ranks 9 on the Mohs Scale of hardness, making it one of the hardest minerals known, surpassed only by diamond. This exceptional hardness allows corundum to be widely used as an abrasive material in various industries, such as manufacturing and construction. Its durability means it can withstand significant wear and tear, making it ideal for applications like grinding wheels and cutting tools.
• Discuss the significance of trace elements in determining the color variations of corundum gemstones like rubies and sapphires.
  • Trace elements play a crucial role in the coloration of corundum gemstones. For instance, the presence of chromium gives rubies their distinctive red hue, while iron and titanium can impart shades of blue to sapphires. This variation not only affects their aesthetic appeal but also their market value, as certain colors are more desirable and sought after than others. Understanding these color dynamics is key for gemologists and jewelers when assessing gemstone quality.
• Evaluate the impact of synthetic corundum on the gemstone market and how it compares to natural corundum in terms of properties and value.
  • The rise of synthetic corundum has significantly impacted the gemstone market by providing an affordable alternative to natural stones. While synthetic corundum shares identical physical and chemical properties with natural corundum, its production process allows for fewer inclusions and more uniform colors. This can lead to a lower perceived value in some markets compared to natural stones. However, synthetic gems are increasingly accepted due to ethical considerations surrounding sourcing natural gemstones, ultimately reshaping consumer preferences.

Related terms

Alumina: A chemical compound of aluminum oxide, often used in ceramics and as an abrasive material due to its hardness.

Sapphire: A precious gemstone variety of corundum that is typically blue, but can come in a range of colors except red, which is classified as ruby.

Mohs Scale:

A scale that ranks minerals based on their hardness, with corundum ranking 9 out of 10, just below diamond.