First a little science about chalcedony (and specifically the variety known here in the southwest as "fire agate"
From Minerals.net
Chalcedony is the form of Quartz that is compact and microcrystalline. It occurs in many different forms, colors, and patterns.
And from fireagate.us @ http://www.fireagate.us/index.shtml
Fire agate, a variety of chalcedony is an all natural gemstone found only in certain areas of Arizona, northern Mexico, and other parts of the southwestern United States. Approximately 24-36 million years ago these areas were subjected to massive volcanic activity during the Tertiary Period. The fire agates were formed during this period of vulcanism when hot water, saturated with silica and iron oxide, repeatedly filled cracks and bubbles in the surrounding rock, often forming a botryoidal (grape-like) growth.
Fire agate gemstones have beautiful iridescent rainbow colors, similar to opal. The colors found within fire agates, created by the Schiller effect as found in mother-of-pearl and fire opal, is caused by the alternating silica and iron oxide layers which diffract and allow light to pass which forms the interference of colors known as fire.
While it is considered a semi-precious gemstone its rarity and beauty has made it a much sought after item. Unfortunately the best localities are private, such as Deer Creek and Slaughter Mountain (on Apache Tribal Lands so DON"T EVEN THINK ABOUT IT!!!), and are strictly off-limits to collecting unauthorized collecting. The sites on Federal (and open) lands such as my favorite Saddle Mountain west of Phoenix, and Black and Round Mountain in the eastern part of Arizona unfortunately have been pretty well picked over the many decades by collectors but can (occasionally) yield a small but colorful specimen of fire agate.
This brings me to one last spot that is private, but open, to collecting - namely the Cuesta Fire Agate Mine near Oatman, Arizona.
http://cuestafireagatemine.ilandwyte.com/cuesta-mine-site.html
Locating alongside old Route 66 southwest of Kingman - where for a fee ($50.00 so it isn't cheap) you can dig, hammer and smash away for the elusive fire agate.
The collecting spots where you are allowed to dig are literally next to the highway
Basically you have to hammer away at the rock to hopefully expose the seams where the silica-rich solutions deposited the chalcedony millions of years ago. So expect lots of hard and dirty work.
So how did I do after 6 hours and several hundred pounds of rock moving?
Well, some nice pieces of "blobby" chalcedony that might polish up nice but definitely nothing that comes close to being fire agates.
Nice stuff. Definitely bigger, clearer and more attractive chalcedony than what I can probably find at Saddle, Round or Black Mountains - but worth $50 and all the effort??? Not really considering what I found. At least I have specimens that at least are true fire agates from the free Saddle Mountain locality. Plus, all you have to do there is find a nice looking spot walk around and pick up the stuff laying on the surface.
Guess I'll stick with Saddle Mountain for now although if I would dig at Cuesta for $10 or maybe $30. Just kind of hard to justify going again at $50 a pop for plain chalcedony even if it is attractive.
BTW here's a piece I picked up off the ground just across the road from my diggings (while I was waiting to head down to check in with the owner)
a look
Maybe not as nice but it was FREE 😀
Give the spot a look if you are in the Kingman, AZ area and feel lucky. Who knows, YOU might find a beautiful chunk of true fire agate. You never know.
Get out and see what gems Mother Nature has waiting for you!!!