How Fire Agate Differs From Opal: An Investigation Into "Rainbow" Stones

Fire agate and opal are similar in that they both reflect iridescent rainbow colors. However, they are also very different sorts of semi-precious stones. The following highlights their more unique properties, in case you were looking for fire agate for sale and run into opals instead.


Opal is formed under low temperatures and is considered a silica stone, while fire agate is formed under extremely high temperatures and is considered chalcedony. It does not take much to form an opal, but it takes a lot to form a fire agate. Simply put, you can create an opal in a lab, but fire agate cannot be reproduced that way. Additionally, opals have been found in cracks and crevices all over the world, but fire agate was only formed in three, extremely hot, southern states in the U.S. and Mexico.

How They Get Their Colors

Opals have any manner of base color, from clear to red and yellow. The depth and deposit of silica flecks in the stone and how those flecks reflect light is what makes an opal sparkle with many colors. You can even see the flecks in the stone when it is placed under a microscope.

Fire agate, on the other hand, is numerous bands of stone all fused together at the precise moment of melting and bubbling before instantly cooling. when you look at a polished fire agate, you can see one or more bubbles of melted stone inside the rock itself. It is the suspended animation of these melted rock bubbles that lend themselves to the multiple colors you see bouncing back out of the surface of the stone. The most desirable fire agates are the ones that have several of these "bubbles" visible in both the unpolished and polished bits of stone.

What You Should Expect to Pay

Because fire agate is more rare and difficult to bring to the surface than opal, you should expect to pay more for fire agate. If all of the favored characteristics are in present in a piece of fire agate, then it may be more expensive than the most precious piece of opal. However, there are bits of fire agate that are less expensive too, and you may be able to find some fire agate for sale on auction sites or in shops in Arizona, Southern California, and New Mexico. If you are visiting any of these three states this year, watch for the fire agate signs along the highways.

Check out places like Studio Rock Shop for your gemstone needs.