Gem Graders

Sphene is a gem that is typically yellow, green, orange or brown in color. Its most notable feature is its incredible fire, which results from its high dispersion.

A drawback to sphene is its hardness (5 to 5.5 on the Mohs scale). It is softer than many gems, which means it should be set in a protective setting and treated with care, especially when worn in a ring.

Seen here is a 16.90 carat oval green sphene.

Courtesy: Kat Florence Atelier

No two gems are exactly alike. Each gem has a unique set of inclusions and crystal deformations that serve as its "fingerprint." Sometimes, these inclusions literally look like fingerprints!

This purple sapphire from Sri Lanka has what's known by gemologists as a "fingerprint" inclusion. These inclusions consist of arrays of tiny fluid or multiphase inclusions that result from the thermal healing of cracks in the growth environment. Inclusions can be used to help determine if a sapphire is natural and whether it has been heat treated. The intact appearance of this inclusion indicates this sapphire is unheated. Field of view 3.74 mm.

Photo: Nathan Renfro/ GIA.