BLUE AZURITE: TUCSON 2016

Who could leave a Tucson Shades of Blue show without taking home a specimen of Arizona azurite.  One of my purchased specimens is a beautiful group of electric blue azurite balls spread on some sort of a gossan matrix.  It is fairly easy to observe, especially with a loupe, that the aggregates are composed of numerous individual crystals of azurite.

Azurite from Morenci mines, Arizona.  Width ~4.6 cm.

Azurite is one of the more recognizable blue minerals since most people associate an azure blue color with the mineral---and they are correct, although the mineral also shades to lighter hues of blue.  Azurite is a secondary copper carbonate [Cu₃(CO₃)₂(OH)₂] found in the oxidized zone above copper deposits where carbonated water reacts with copper minerals, or with solutions of copper sulfate or copper chloride reacting with limestone (www.MinDat.org).  The crystals are Monoclinic, commonly quite complex, and are displayed in several different forms with over 100 recorded examples (Handbook of Mineralogy, Mineral Data Publishing, www.rruff.info).  My specimen is composed of individual tabular crystals formed into spherical aggregates while other crystal examples commonly are prismatic.  Crystals are transparent to translucent, vitreous in individuals but less so (subvitreous) in aggregates.  The streak is a very pale blue and the crystals have a hardness of around 3.5-4.0 (Mohs).

Photomicrograph of above specimen.  Azurite aggregates composed of individual tabular crystals.  The center aggregate is ~ 5m mm in width.

The specimen that I purchased came from the Morenci Mine, Copper Mountain District, Greenlee County near Clifton, Arizona.  Morenci is one the largest copper producers in the U.S. and the ore, like many southwestern copper mines, is a porphyry copper ore body (large volumes of ore allows mining with copper content of less than 1%). 

At Morenci the reserves contain: millable ore grades at 0.48% copper, crushed ore runs 0.51% copper, while the large deposits of leachable ore averages 0.16% copper. These low figures contrast with the early mining of oxides where the copper content averaged about 20%. 

In a typical copper porphyry ore deposit, such a Morenci, pyrite [FeS₂], chalcopyrite [CuFeS₂], bornite [Cu₅FeS₄] (not important at Morenci) and chalcocite [Cu₂S] are the major copper sulfide minerals in the Primary Zone.  In some copper ore deposits, such as Morenci, other Primary Zone non-copper minerals are also present and sometimes mineable: molybdenite (MoS₂; in production), galena (PbS), and sphalerite (ZnS).

These Primary Zone minerals, in ore deposits, form from superheated aqueous solutions (hydrothermal) that originate at great depths and then migrate upwards where deposition begins, usually in lime rocks..  In some cases, where the sulfide minerals are near the surface, low temperature water (meteoric) oxidizes and alters the Primary Zone minerals and dissolved elements are carried downward and may precipitate out and form new minerals.  These Secondary Zone minerals form both above and below the water table.  The minerals that form above the water table are stable in an oxidizing environment and include minerals such as malachite [Cu₂CO₃OH], smithsonite [ZnCO₃], cuprite [Cu₂O], azurite [Cu₃(CO₃)OH₂], pyromorphite [Pb₅(PO₄0₃Cl], atacamite [Cu₂Cl(OH)₃], chrysocolla [(CuAl)₂H₂Si₂O₅(OH)4-nH₂O], native copper [Cu], and tenorite [CuO]. Minerals precipitating out below the water table, in a reducing environment, are mostly sulfides like covellite [CuS], and chalcocite [Cu₂S]. Above in part from Rakovan (2003).

The Morenci deposits were mined underground until the 1930s and then converted to open pits (www.mining-technology.com/projects/morenci).  In 2015 copper production at Morenci was 902 million pounds and the company employed over 3,200 people (www.freeportinArizona.com). 

Morenci became a critical part of Phelps Dodge and Company in 1881 but is now part of Freeport-McMoRan Inc. with Sumitomo Metal Mining Company a substantial minority partner.  

Aerial view of the open pit mines at Morenci.  Photo courtesy of www.freeportinarizona.com.

Morenci is also famous for once producing, via the “miner’s lunch box” method, a sky-blue turquoise in a pyrite matrix.  If I understand correctly, vintage Native American turquoise jewelry is coveted by collectors and is quite expensive.  I also believe that Morenci produced (produces?) minor amounts of silver and gold as accessory minerals; however, I have been unable to locate production figures.

REFERENCES CITED

Rakovan, J., 2003, Hypogene and supergene: Rocks and Minerals, v.78.

TUCSON MAIN SHOW 2016

 

Well, the big day finally arrived---the opening of the 62^nd Annual Tucson Gem and Mineral Show.  I was in line early on opening day, the 11^th of February.  The theme of the 2016 show was Shades of Blue: Minerals of the World.  I was guessing the displays would include a variety of sapphires, topaz, fluorite, and azurite.  As it turned out, that was a pretty good estimate; however, I did not use up much brain power with that pronouncement! Much of the “fun” at the Tucson Show always includes the innovative names for the display cases.  The “Shades of Blue” theme brought out such titles as: The Birth of the Blues, Rhapsody in Blue, Shades of Blue, It’s a Blue, Blue, Blue World, Maine’s Got the Blues, Colorado Blues, Blue Minerals of the World, Blue Hues from Arizona, Mother Nature Sings the Blues, Arizona Type Blues, and the rather mundane Azurite from Russia.  Of course my favorite case was displayed by Jack and Kaye Thompson direct from the Colorado Springs Mineralogical Society. 

Thumbnails exhibited by Jack and Kaye Thompson.  My camera did not record this display well so the above photo is from the website www. Minerals.net and is copyright by Hershel Friedman and Minerals.net.

During most visits to the Show I find very few minerals within my purchasing budget.  I usually come home with a specimen or two but attend the Show mostly to see the fantastic display cases filled with minerals, and to ogle at the “for sale” minerals often priced at many tens of thousands of dollars.  Everything about the Show is exciting.

The early morning line on Day 1 at Tucson 2016.

Blue Australian opals often have an amazing opalescent glitter.

Lapis lazuli is a combination of many minerals; however, the blue color is always prevalent. 

 

A selection of blue faceted and cabbed gems. 

Who could ask for nicer malachite?  They are not “blue” but are fantastic copper specimens. 

Take your choice:  blue aquamarine or a hunk of gold. 

Some really nice jewelry.

Some of the nicest shades of blue are found in fluorite specimens at from many localities.

The mines at Bisbee, Arizona are famous for their blue secondary minerals.

 

I would love to have this specimen of azurite and malachite from Morenci, Arizona.

Krohnkite is a rare copper sulfate.  This specimen came from the Chuquicamata Mine in Chile.

BLUE CARLETONITE: TUCSON 2016

One of the big venues of the Tucson Shows is held at the Hotel Tucson City Center (HTCC).  The 292 vendors come from around the world and sell a variety of minerals, rocks, fossils, shipping boxes, books etc.  Unlike some venues, for example Kino, the vendors are selling treasures with a geology connection.  I believe these vendor standards are due to the promoter, Coloradan Marty Zinn.

Many of these HTTC vendors are selling high end minerals and fossils.  For example, Joe Dorris from Colorado Springs had some great specimens of amazonite and smoky quartz pulled from his discoveries near Lake George west of the Springs.  Other dealers sold a variety of very fine, museum-quality, dinosaur casts.  If buyers wanted the “real thing” Glen Rockers of Hays, Kansas, offered some very nice vertebrate fossils he collected from the Smoky Hill Chalk Member of the Niobrara Formation (Cretaceous).  Rockers collects on private land in western Kansas; therefore, the collection of vertebrate fossils is quite legal.  It is only on public land that the collection of vertebrate fossils is illegal.

This vendor had a great display of blue tanzanite, the gem variety of the mineral zoisite. I find it interesting that many brochures and jewelers comment on the great scarcity of tanzanite and how the mining of the mineral is just “drying up.”  However, there are thousands of specimens, both raw and faceted, for sale each year at the major shows.  I would like purchase a nice piece; however, the specimens are well out of my price range!

The vendors at the show display their wares in the large ballrooms as well as most of the hotel rooms. 

This is an interesting specimen of quartz.  Does not look like quartz?  Well it is a pseudomorph after anhydrite.

Every kid interested in dinosaurs would love this replica of a poor ole plant eater being zipped by a couple of small raptors.

Nice therapod (meat eater) skull.  Note those massive shearing Nice therapod (meat eater) skull.  Note those massive shearing teeth.

This display is available every year and I love it.  There are fake Moroccan trilobites, and other critters, all over the place.  It is hard to say but a good guess might be 75%? 

This is a “real” fossil from the western Kansas chalk beds (Niobrara Formation): Xiphactinus, the “Bulldog Fish.” 

Glen Rockers of www.paleosearch.com always has nice displays of Cretaceous vertebrate fossils from the Kansas chalk beds.

A portion of a fossil cycad collected from Lower Cretaceous rocks in the southern Black Hills of South Dakota.  Cycad National Monument was created in 1922; however, without much supervision (by the local ranchers only) collectors simply pilfered most of the available specimens.  The Monument was decommissioned in 1957.  When I visited the area in 1966 a few pieces of the fossil plants were still around.  Specimen is from the Black Hills Institute of Hill City, South Dakota.

Before leaving for Arizona and the Tucson Shows I received my copy of Rocks and Minerals and was delighted the issue centered on “blue minerals” to correspond with the theme of the main Tucson Show.  One of the magazine articles was a description of the mineral carletonite, a new one for me [KNa₄Ca₄Si₈O₁₈(CO₃)₄(OH,F)-H₂O].  I noted it was such a gorgeous royal blue color but sort of put it aside in my mind as I saw descriptions such as rare, expensive, and “finding a fine specimen of carletonite today is nearly impossible.  And the outlook for the future is not promising…” (Pohwat, 2016).

Photomicrographs of carletonite with enlargement above.  Width FOV bottom ~8 ,mm.  Both royal blue and clear material can be observed.  

Carletonite was originally described as UK15 (for unknown) and was not named until 1971.  The mineral is only known from one locality, Poudrette Quarry Mt. Saint-Hilaire, in Canada.  The quarry has been off limits to collectors for several years and the main collecting pegmatite for carletonite is now flooded; therefore, with encouragement like that I did not expect to even see crystals of carletonite, let along see specimens for sale in my price range.  To my great surprise, as I was strolling along the motel rooms, I stopped to observe some “sale specimens” of a Canadian dealer.  Wow, there was a specimen of carletonite in my price range ($7).  It probably is not the best specimen in the world; however, it certainly qualifies as an interesting mineral in my collection since any specimens of carletonite on the market today come from older collections.

The colorful carletonite is that beautiful royal blue color although some crystals are colorless, pink or light blue. Many of the crystals are zoned with blue centers surrounded by colorless crystalline material.  This type of zonation may be seen in photos of my specimens.  The crystals range from transparent (colorless material) to translucent (blue material) and have a vitreous luster.  They are somewhat soft at 4.0-4.5 (Mohs) with a white streak.  The crystals (Tetragonal) tend to be prismatic although this feature is difficult to discern on smaller fragments.

Mont Saint-Hilaire is a fascinating mineral locality.  MinDat lists 404 valid minerals collected from the quarries with 63 of the species being first described from the locality.  What makes the locality so special? Powhat (2016) noted the dominant rocks at Mont Saint-Hilaire are feldspathoidal seyenite, an igneous intrusive rock composed of alkali feldspar, a feldspathoid, and accessory minerals. The feldspathoid minerals are usually sodalite (sodium aluminum silicate chloride) and nepheline (aluminosilicate of sodium and potassium).

Feldspathoid-rich rocks (wherever they occur) often produce a great variety of rare minerals, including carletonite.  A glance at MinDat will often amaze the rockhound since the list of minerals (the 404) is a lesson in “what in the world is that mineral?”  Besides the seyenite, carletonite also evidently occurs in metamorphosed siliceous limestone: marble (www.webmineral.com).

REFERENCES CITED

Pohwat, P.W., 2016, Carletonite, Mont Saint-Hilaire, La Vallee-du-Richelieu RCM, Monteregie, Quebec, Canada: Rocks and Minerals, v.91, no. 1.