A Mexican agate, showing only a single eye.  Included matter of a green, golden, red, black or other color or combinations embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to dendritic or moss agate (named varieties include Maury Mountain, Richardson Ranch, Sheep Creek and others). Dendritic agates have beautiful fern like patterns on them formed due to the presence of manganese and iron ions. Occasionally agate fills a void left by decomposed vegetative material such as a tree limb or root and is called limb cast agate due to its appearance.

Turritella Agate

Turritella agate is formed from fossilized Turritella shells silicified in a chalcedony . Turritella are spiral marine shells. Similarly, petrified wood, coral, and other remains as well as porous rocks can also become agatized. Agatized coral is often referred to as  Petoskey agate

Certain stones, when examined in thin sections by transmitted light, show a diffraction spectrum due to the extreme delicacy of the successive bands, and they are named rainbow agate.

Other forms of agate include carnelian agate , Botswana agate, Ellensburg blue agate, blue lace agate, plume agate (such as Carey, Graveyard Point, Sage, St. Johns, Teeter Ranch, ....), fire agate (which seems to glow internally like an opal) and Mexican crazy-lace agate.

Graveyard Agate