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 23 hours, 26 minutes ago in Jewelry & Precious Stones - Other
0 Answer(s)