GS PrelimsScience and TechnologyGeneral Science2008

What are Rubies and Sapphires chemically known as?

Silicon dioxide

Aluminium oxide

Lead tetroxide

Boron nitride

Correct Answer: Option B

Explanation

1. Rubies and Sapphires are precious gemstones. 2. Both are varieties of the mineral corundum. 3. Chemically, corundum is crystalline Aluminium oxide (Al2O3). 4. The different colors arise from trace impurities: chromium impurities cause the red color of rubies, while iron, titanium, chromium, copper, or magnesium impurities cause the blue, yellow, pink, purple, orange, or greenish colors of sapphires. 5. Silicon dioxide is quartz. Lead tetroxide is red lead. Boron nitride is a synthetic compound.

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