General:
* Chemical Formula: Al₂O₃ (Aluminum Oxide)
* Crystal System: Trigonal
* Hardness: 9 on the Mohs Hardness Scale (second hardest mineral after diamond)
* Color: Varies widely, including red, blue, green, yellow, pink, purple, orange, brown, and black. Colorless corundum is also found.
* Luster: Vitreous (glassy)
* Cleavage: None
* Fracture: Conchoidal (shell-like)
* Transparency: Transparent to translucent
Notable Features:
* Gemstones: Corundum is the source of two highly prized gemstones: ruby (red) and sapphire (all colors except red).
* Trace Elements: Trace elements are responsible for the various colors in corundum. For example, chromium gives rubies their red color, while iron and titanium cause sapphires to be blue.
* Occurrence: Found in metamorphic and igneous rocks, often associated with other gemstones like emeralds and diamonds.
* World's Largest: The largest corundum crystal ever found was a 500-pound sapphire, discovered in Madagascar.
* Industrial Uses: Corundum's hardness makes it valuable for industrial applications like abrasives, grinding wheels, and watch bearings.
* Mythology and Folklore: Corundum has been valued for its beauty and believed to possess mystical powers for centuries.
Interesting Facts:
* Star Sapphires: Some corundum crystals contain needle-like inclusions of rutile that create a star-shaped reflection, known as "asterism."
* Star Rubies: These are less common than star sapphires, but equally impressive.
* "Padparadscha" Sapphires: A rare, highly sought-after variety of sapphire with a unique salmon-pink to orange color.
* Corundum's "Rainbow": The variety of colors in corundum is truly remarkable. It is one of the few minerals that can be found in practically every color of the rainbow.
These are just a few facts about corundum, a fascinating and valuable mineral. It continues to amaze and captivate people with its beauty and versatility.
