Dendritic agate is an unusual and a very attractive whitish-gray or colorless variety of chalcedony. It has unique dendrites or marking resembling a tree or fern. This name dendritic agate is used for this type of gemstone.

The dendrites found in the dendritic agate are the inclusions of iron or manganese which are usually brown or black in color. Though dendrites appear to be of organic nature due to their fern-like structure, they are actually inorganic. They are formed at fine fracture surfaces through crystallization of weathered solutions of the neighboring rock.

The dendrite inclusions occur at various depths in the rough stone. Dendritic agate can be very tricky to cut. The stone needs to be cut carefully to expose the most interesting patterns.