Opal is known for its unique display of flashing rainbow colors called play-of-color. There are two broad classes of opal: precious and common. Precious opal displays play-of-color, common opal does not.

Learn about opal's durability and how to care for your opal jewelry.

Individual opals are as diverse as snowflakes or fingerprints and can vary widely in appearance and quality. Learn about the factors that make opals so desirable!

本文摘自《宝石与宝石学》（1991 年冬季刊），是《宝石与宝石学》外部发表的重要宝石学相关文章的摘要汇编。