What is Amazonite?
No, it's not the answer to a Jeopardy question. Amazonite is a type of microcline feldspar colored blue to green by small amounts of interstructural lead, and possibly affected by natural radiation over a long geological period. Previously, it was reported here to be the official state mineral of Colorado. This is in error, and we're not certain where this rumor originated, perhaps an old list in Lapidary Journal years ago. Just recently (Spring 2002),rhodochrosite was named official state mineral. Nonetheless, amazonite is a deserving species for this designation, so I personally would have liked to see both as co-state minerals. Both occur in beautiful world-class minerals here. Everything official in Colorado is pretty much blue...blue spruce (the state tree), blue columbine (the state flower), blue aquamarine (the state gemstone) and so on. So it would fit right in. About the only thing that isn't is the stegosaurus (the state fossil). But then of course it could have been blue while it was still alive!
Now ordinary microcline is normally not too exciting. Without the lead content (from the concentration of rock juices that formed the pegmatite environments) microcline tends to be ordinary white. Well, it can be pink or beige, but that's just because of iron content. Iron is an all-too-common element in the Pike's Peak batholith granite pockets, or miarolitic cavities as scientists call them. The iron often forms hard-to-clean stains and crusts on many of the crystals found therein, and even below the surface skin of some smoky quartz and topaz crystals. When they're below the surface you can't clean them without destroying the crystal itself unless there remains a channel or entryway from the outside. Anyway, Bill Hayward (famous Colorado collector who has been on the scene forever it seems) once told me that there was actually no such thing as pink microcline. If you cook the pink ones long enough in oxalic acid (which removes the iron) they will eventually turn white. Sure enough.
To my eye, the deeper the blue-green the color in the crystal the more greenish it often tends to look. Crystals can go from pale blue to sky blue to dark blue to very dark blue-green. In many amazonite localities around the world, the amazonite occurs in anhedral (formless, without crystal faces) masses often with white contrasting perthite inclusions which makes great cutting rough. I've seen good stuff from Russia, Africa, and Amelia, Virginia. If you orient the rough so that the cleavage plane is on top of the cabochon it has a cool silvery-white sheen on it reminiscent of moonstone (another type of feldspar). Most of the Colorado material, on the other hand, forms euhedral (well-formed), or subhedral (not so well formed) crystals, as does Brazilian material. Brazil seems to be the place where monster crystals of all sorts come from. But I've seen Colorado crystals as big as the ones I've seen from Brazil (OK, admittedly rare).
Well, except for a few monster crystals with dark green/black tourmaline on
them that came to light around the late 90's. Most of the Colorado material forms in the Pike's Peak granite batholith at various well-crystallized places. The most famous is Crystal Peak. This is a huge area. The downside is that considerable quantity of the land was developed into cabin and home areas some years ago. You can always tell you're getting close by all the "Keep Out, No Trespassing" signs you see. Rockhounds have not always left a good impression on the local residents. Fortunately, there is also a very large area of national forest left nearby to prospect in. There's a downside here too though. There are mining claims all over everywhere. It is difficult or impossible in some places to tell if you are on an active claim or not. Recent changes in mining laws have left many of the less productive areas unclaimed. However, if the signs and claim posts are fairly new and it looks like it's been recently worked, it probably is an active claim. It's better to err on the safe side here. Some claim-holders have been known to be armed and get a bit hacked off at trespassers!
is famous for plates and groups of crystals, some with the highly desired smoky quartz crystals which offset the blues of the amazonites so beautifully. Some crystals from here have alternating white stripes or white caps which are also very showy, and the little hemispheres of bladed white clevelandite feldspar on some specimens add to the effect. Crystal Peak smokies can be very beautiful in their own right, although average ones have little value because of their abundance. The best are long and slender and show evidence of twinning and are gem quality. Color varies from pale to deep black (morion). The finest are a medium cola or rootbeer color in transmitted light. They can be up to a foot long or even more. A typical amazonite is an inch or two long, but I have seen some up to a foot long.
Topaz is not real common here, but does occur in some spots. They are usually white or blue. Fluorite cubes or octahedrons in blue, white, and purple are fairly common (Occasionally green or other colors). They range up to 3 inches or so. I found a few small phenacites here in the early 70's implanted on smoky quartz crystals that a road grader hit! Other minerals can sometimes be found as well. Micas and goethite are reasonably common, but most other others are rare. Sometimes columbite/tantalites can occur, as well as onegite and amethyst.
Prospecting is done by following "float" or pieces that have eroded down the hillside and tracing them back up to the seam or pocket they came from. At least that's the theory. Good crystals can often be found in old dumps. The reasons are that the materials come out of the pockets usually covered in "red mud", which is really a type of clay, an alteration product of the feldspars. It serves a useful purpose of protecting the crystals from some damage due to weathering, earth movements, and extraction. However, the gooey clay also hides features and sometimes causes people to throw out small crystals or pieces that they might normally take home. Another thing is that not everyone is looking for the same things. Old dumps can be especially fruitful in that back in the early years the smaller crystals may have had little value then. They may have only been interested in the monsters or the finest qualities.
It is important when prospecting to make sure you don't damage the crystals when removing them--it devalues them greatly.
Smokies in particular are subject to having their terminations chipped
during extraction. Some light damage is often inevitable, but since plates of attached crystals are much rarer and much more valuable than single crystals, it is very foolish to remove crystals from their attached matrix (oftentimes the crystals are already cleaved off the matrix in the pocket or the matrix is all cracked up). The proper procedure here is to remove the whole matrix with crystals intact (if solid) and with no damage. This is a real art and often a LOT of careful work with the proper tools.
Matrix pieces can then be properly trimmed by an expert with the proper
equipment back at the shop, if necessary, and if it is deemed wise after
some cleaning and study. It is heartbreaking to see the remains of a fine pocket all beat up by overzealous rockhounds without the proper tools, collecting knowledge or patience.
Other famous spots are...
Crystal Park, right outside of Manitou Springs. It is famous for bright, dark blue crystals, and some funky associated minerals like phenacite, topaz, and the like. One look at the routes to the collecting area here shows you why not too many people still work it. The road up there is privately developed housing and there is a guarded gate across the road. You must own property up here (or be a guest) to use this road. The other way up involves a very long (several miles), STEEP hike up from the east. The Crystal Park area also encompasses the collecting sites of Specimen Rock, Sentinel Rock, and Cameron Cone.
There has also been some amazonite, smoky quartz,
fluorite, and other minerals found nearby at Stove Mt. and
St. Peters Dome, along with many rare earth and
unusual minerals like zircon, bastnaesite, riebeckite, and astrophylite.
This area is very steep and accessible from the old Gold Camp Road trail.
north of Bailey. The crystallized area here is in what is known as the Rosalie Lobe, sort of an isolated offshoot of the main granite batholith. I first became acquainted with the area because of former Denver rock shop owner Don Cook. He was one of the original prospectors. The Littleton Gem and Mineral Club own the two main claims here, and club member Lee McKinney two more adjacent ones. Collecting is for club members or by permission only. Another claim some distance away is the Black and Blue Claim owned by miner friend Ken Gochenour of Healdsburg, CA. It was discovered by two other digging friends, Robert and Doris Drisgill of Colorado Springs. Some terrific large crystals and plates have come from all of these diggings, many with smokies, and some with champagne topaz! Amazonite from here is often sort of mottled and never real dark, almost always sky blue in color. Often the terminations will have a fairly medium-dark spot on them right in the center of one of the faces, while the rest of the area will be considerably lighter. Side faces are always lighter colored and often show slight to medium etching.
I once hit an eroded pocket on the club claim that had over 4,000 carats of champagne topaz in it. The topaz was coated on some faces with an almost impossible to remove white crust, and the champagne color faded readily in the light. However, some of the topaz found by Tom Odiorne and others implanted on the sides of amazonite crystals still retains it's sherry color. I don't know if they keep them in the dark most of the time or what. Other minerals are not common, except goethite replacing siderite crystals, but some secondary growth dark amethyst has been found here.
Other spots are
Wigwam Creek area (claimed by the Denver Gem and Mineral Guild), and rarely,
Devil's Head peak. Wigwam produced the largest gem topazes ever found in Colorado (white and sherry) around 20 years ago. Most of the amazonite from here is pale to medium color. Smokies are fairly common, but the majority I have found or seen are not very good. They often seem to have one or more sides of poor quality. There are some good exceptions, however, and there are occasional finds of groups or (amazonite/smoky) combinations. Devil's Head is famous for good large smokies and topaz (white, blue and sherry), but good amazonite is quite rare there. Most of the microcline is pink or beige (white). But good color does exist, and I have dug a small amount in old dumps. There was evidence that the original finder had acquired some fine combination groups. This is a large area off the Rampart Range Road, and a good place to get temporarily turned around in if you wander too far afoot. The areas south and southwest of the peak seem to be the most highly mineralized. Fluorite is not uncommon and tiny amounts of good amethyst and citrine have been found here.
Tarryall Mountains to the west. There is no amazonite there, but some fair to good smokies, and the best overall gem topaz hunting in the state. Some spots are alluvial, like the old Bob Moore dig, while others are hilly or in steep granite spires. Topaz here is usually white or blue.
Glen Cove off the side of Pike's Peak is a small area, but famous for topaz (white, sherry, blue) and smokies and some good amazonite. This is where the late mineral collector extraordinaire Ed Over successfully collected using ropes to repel the cliffs. There are a few other scattered small areas or "secret" areas as well.