The most common type of agate in existence, fortification agate carries crystallized bands which flow along the cavities inside the stone, which means when you slice it, these look a lot like the cross section you would see on an old tree stump – full of concentric rings.
A rarer variety than fortification agate, fire agate carries a singular iridescence. Being old stones that were formed over millions of years of volcanic activity, these agates look fiery and have a reddish-brown coloring that often includes color swirls. They cost more but bring value to match.
As the name implies, this agate variety carries beautiful lace, along with sophisticated swirls and hoops. This is the rarest agate you will find in the market, with the blue and red varieties being the most highly priced.