What are the key differences in the hardness and optical properties among various types of precious stones, such as diamonds, sapphires, rubies, and emeralds?

What are the key differences in the hardness and optical properties among various types of precious stones, such as diamonds, sapphires, rubies, and emeralds?
Admin on August 06 2025 at 05:27 PM in Jewelry & Precious Stones - Other
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