Corundum: The Gemstone that's Tough Enough for Diamonds

Imagine a mineral so tough it can scratch almost anything, so beautiful it adorns crowns and rings, and so versatile it finds uses in everything from jewelry to sandpaper. That's corundum, a remarkable material with a rich history and fascinating properties.

What is Corundum?

Corundum is a crystalline form of aluminum (aluminium) oxide, meaning it's made up of tiny, repeating units of aluminum (aluminium) and oxygen atoms arranged in a specific structure. This structure gives corundum its incredible strength and hardness, making it the third hardest mineral on Earth, behind only diamond and moissanite.

Etymology:

The word "corundum" comes from the Tamil word "kurundum", which translates to "ruby" or "red corundum." This connection highlights the historical association of corundum with its most famous variety, the ruby.

Properties of Corundum:

• Hardness: 9 on the Mohs scale (diamond is 10)

• Density: High, making it heavy for its size

• Luster: Adamantine (brilliant like a diamond) or vitreous (glassy)

• Cleavage: None, meaning it doesn't break easily in specific directions

• Color: Naturally colorless, but impurities can create various colors

The Gemstone Chameleon:

While pure corundum is colorless, trace amounts of other elements can paint it a dazzling array of colors. Here are the two most famous varieties:

• Ruby: The presence of chromium gives ruby its fiery red color, making it one of the most prized gemstones.

• Sapphire: All other colors of corundum are called sapphires. Iron and titanium create blue sapphires, while other elements like vanadium and magnesium can produce yellow, green, pink, and orange sapphires.

A rare and highly sought-after variety is the padparadscha sapphire, which exhibits a unique pink-orange color.

History of Corundum:

Corundum has been admired and utilized by humans for millennia. Evidence suggests its use in jewelry and tools dating back to ancient civilizations in Egypt, Greece, and Rome.

• Ancient Egyptians: Used corundum for abrasives and even carved scarabs and other decorative objects from it.

• Greeks and Romans: Believed sapphires protected their wearers from harm and used them in jewelry and amulets.

• Medieval Europe: Associated sapphires with royalty and believed they symbolized truth, justice, and wisdom.

Beyond Gemstones: The Industrial Uses of Corundum:

While prized for its beauty, corundum's remarkable hardness makes it valuable for industrial applications as well. Here are some examples:

• Abrasives: Crushed corundum, often called emery, is used in sandpaper, grinding wheels, and other abrasive materials for polishing and shaping various objects.

• Refractory materials: Corundum's high melting point makes it ideal for lining furnaces and crucibles used in high-temperature industrial processes.

• Sandblasting: Corundum grit is used for sandblasting applications to clean and roughen surfaces.

• Laser crystals: Synthetically grown corundum can be used to create laser crystals used in various technological applications.

The Future of Corundum:

With its unique combination of beauty and strength, corundum continues to play a significant role in both the gem and industrial worlds. As technology advances, we can expect to see even more innovative uses for this remarkable mineral.

Interesting Facts:

• The largest faceted sapphire ever discovered is the "Star of India", weighing over 563 carats and housed at the American Museum of Natural History in New York City.

• The largest ruby ever mined is the "Rajaratna", found in Sri Lanka and weighing over 3.500 carats.

• Synthetic corundum, including rubies and sapphires, can be grown in laboratories under controlled conditions. These stones are often indistinguishable from their natural counterparts and are widely used in jewelry.

Conclusion:

Corundum is a fascinating example of how nature can combine beauty and functionality. From adorning the fingers of royalty to helping build modern technology, this versatile mineral continues to captivate and inspire us.

Further Exploration:

If you're interested in learning more about corundum, you can visit museums with mineral collections, attend gem shows, study our specimen in 3D view here at www.historytimecapsules.com or research online resources. You can also explore the world of jewelry and see how corundum is used to create stunning and timeless pieces.