Decorative, patterned forms of agate are excellent natural gems. This variety of chalcedony takes on a number of forms, most commonly banded with color, but sometimes with lovely inclusions that look like moss, trees, or even entire landscapes. Agate, the alternative birthstone for Geminis, is affordable even in large sizes. It can be used for jewelry or to make decorative items. Before your next agate buying trip, learn more about the rare and beautiful forms of this gem material.

Agate Buying and the Four Cs

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


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.


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…