The other one is peridot, but spinel is radically different from it in terms of color.
While the former comes in a yellow-green shade, spinel is warm with red, pink, purple, yellow, orange, and brown. Sometimes, it also comes in blue or black, and in those cases, usually steals the spotlight from any accompanying mounted diamonds.
“Spinel” derives from the Latin word spina, meaning “thorn”, because it has a pointed shape. The vibrant color it carries can cause you to mistake it for ruby or sapphire. Former AGTA CEO Doug Hucker once revealed that jewelers were only able to distinguish spinel from these gems by the 18th Century when technology had advanced enough to make this possible. Basically, rubies and sapphires are made of corundum. Spinel, on the other hand, is mainly an oxide mineral, and normally found as crystals.
Royalty has been known to seek out spinel in the past, mainly because of the way the stone resembles ruby and sapphire. In fact, the Imperial State Crown of Great Britain carries a 170-carat spinel, called the “Black Prince Ruby”.