Agate Buying and the Four Cs

The IGS agate value listing has price guidelines for agate, fire agate, and blue chalcedony cabochons.

Color

Agates form in a wide variety of colors due to trace metals in the mineral’s chemical makeup. Vivid natural colors in agate will have a higher value than colors that are less intense or artificially dyed. Blue and green hues are the least common. They will command somewhat higher prices than red and yellow colors.

Clarity

Most agate is translucent, with a few transparent or opaque specimens.  Still, the gem should be eye-clean, without large inclusions or fractures.

Moss, dendritic, and plume agates are the exception. Here, the inclusions create beautiful natural patterns, the hallmark features of these stones.

Cut

Agate cabochons or slices should attractively showcase the stone’s patterns. A proper cut will enhance the banding or inclusions to create a beautiful and appealing piece.

For carved or sculpted pieces, creative use of the natural patterns is most important. Accordingly, the artistic use of agate will add a premium to this gem’s cost. (Most of the expense is due to artistry and skill rather than the stone itself).

Carat

Found in all sizes,…