Sapphire
Definition and meaning of Sapphire in chemistry.
Sapphire is a naturally occurring, highly valued crystalline variety of the mineral corundum, consisting almost entirely of aluminum oxide (Al2O3).
In more detail
While pure corundum is strictly colorless and transparent, trace amounts of transition metal impurities give natural sapphires their famously vibrant colors. For instance, the simultaneous presence of iron and titanium impurities results in the classic deep blue sapphire, whereas chromium impurities fundamentally turn the corundum into the distinct red gem known as ruby. Sapphires are widely renowned for their exceptional physical hardness, rating a solid 9 on the standard Mohs scale, which makes them remarkably scratch-resistant and durable. Because of this resilience, synthetically produced sapphire is widely utilized outside of jewelry in scientific instruments, luxury watch faces, and high-durability optical windows.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Chemical Formula | Al2O3 (with impurities) |
| Mineral Type | Corundum |
| Hardness | 9 on the Mohs scale |
Synthetic sapphire is commonly used as the robust physical substrate for growing gallium nitride in the manufacturing of commercial blue light-emitting diodes (LEDs).
Frequently asked questions
What is the chemical difference between a ruby and a sapphire?
Both are strictly forms of corundum (Al2O3); rubies specifically contain chromium impurities, while sapphires contain other transition metal impurities like iron or titanium.
Can sapphire be made synthetically?
Yes, large quantities of synthetic sapphire are produced industrially using thermal processes like the Verneuil method for optics and electronics.