Spinel

Spinel has a hardness range of 7.5 to 8. These beautiful gems make excellent, durable jewelry stones in many colors. Prior to the 20th century, many spinels were identified as rubies or sapphires. Spinel, Sri Lanka, 4.93 cts. Photo © Joel E. Arem, PhD, FGA. Used with permission.

Article: How to Polish Gems of 7-8 Hardness: Survey Results

Credit: Joel E. Arem, PhD, FGA