HENDERSON CREEDITE,ANTERO MOLY, CHONDRODITE, AND WOODSTOCK

It has been one of those weeks where the hot weather has sort of fizzled my brain and sent me into memory lane.  Of course, 94 degrees with 10% humidity (Colorado) is not really “hot” compared to my former home in Kansas where my friends were suffering in 107 degrees.  My heat-addled mind often “remembers” in decades and so it was this time, 50 years ago—the summer of 69.  This time period was easy to remember since the country was in an uproar over events in southeast Asia, a great geology scenery movie starring Paul Newman as Butch Cassidy and introducing Robert Redford as the Sundance Kid was released, the U.S. put a “man on the moon” in late July, Charles Manson and his groupies went on a killing rampage in early August, and 400,000+ mostly young people converged on a farm in upstate New York to attend a music festival—Woodstock.  Lately I have been watching “documentaries” on the tube about Woodstock and it brought back many memories.  I liked much of the music (not a fan of Jimi Hendrix tho) but as a small-town kid from conservative Kansas I simply could not really identify with the drugs and seemingly open sex for everyone--was the latter really true?.  What I could identify with was the fear (and reality) of so many young men waiting for the county draft board to ship them off on a bus for a make-believe physical exam, and then off they went to southeast Asia.  If a male college student flunked just one class, it was, as Buffalo Springfield sang:   Paranoia strikes deep / Into your life it will creep, It starts when you're always afraid / Step out of line, the men come and take you away.

I lost friends in the conflict and the mind, intellect, reasoning and judgment of an entire generation was affected and remembered; our country has never healed. 

I’m fed up to the ears with old men dreaming up wars for young men to die in.     George S. McGovern

For the “hippie” pilgrims (the term of the press) of the day, Woodstock was a break in the reality of the war and a time where one, for three days, could just forget and kick back.  Let their mind rest. After the concert was over it was back to the reality of draft boards, physical exams and long plane rides:

Well, come on all of you, big strong men,

Uncle Sam needs your help again.

He's got himself in a terrible jam

Way down yonder in Vietnam

So put down your books and pick up a gun,

We're gonna have a whole lotta fun.

And it's one, two, three,

What are we fighting for ?

Don't ask me, I don't give a damn,

Next stop is Vietnam;

And it's five, six, seven,

Open up the pearly gates,

Well there ain't no time to wonder why,

Whoopee! we're all gonna die.

                                                         Country Joe and the Fish

But again, I was just the small-town kid, married for two years and working hard on a graduate degree at the University of Utah.  I had neither the time nor the money nor the inclination to tromp off to New York.  In fact, I just looked at my field book/notes and noticed that August 15-18 I was tromping around in rural southwestern Wyoming mapping some rock units and collecting vertebrate fossils.  I had been walking and searching all summer and had been concerned that a lack of fossils would not allow me to complete a dissertation and then I was in trouble, big trouble.  However, in mid-August the stars were aligned correctly, and I stumbled across an opening in the sagebrush north of Evanston and saw bone chips and part of a turtle scute. My heart fluttered as I sank to my knees and stuck my face to within six inches of the ground and started seeing small mammal teeth and bones.  I knew at that moment “things” were going to be OK and I could handle the rest of my graduate academics.  Maybe, as a popular 5^th Dimension 1969 song belted out, we were in the Age of Aquarius and Jupiter-Mars aligned with my fossil find!

When the moon is in the Seventh House
And Jupiter aligns with Mars
Then peace will guide the planets
And love will steer the stars
This is the dawning of the age of Aquarius
Age of Aquarius
Aquarius
Aquarius

So, the summer of 69 was an important time in my life.  Wow, 50 years ago.  The summer of 2019 (with some poor music) has not been as eventful but never-the-less has been interesting and I always look forward to the numerous rock and mineral shows scheduled for the summer months.  A week or so ago (I am still writing a month later) I was able to wander up to Woodland Park for the show and enjoyed visiting with many vendors and picking up a few specimens.  I mean how can one attend a mineral show and not come home with something?

I have a detailed posting on pyrrhotite (July 28, 2014) so will not repeat that information.  In fact, I really did not need another specimen of the iron sulfide (Fe₇S₈); however, this was a very nice piece, cheap, and available.  Pyrrhotite is sort of a strange mineral is that it is magnetic and easily attracts a magnet as a variable amount of iron vacancies in its crystal structure. The specimen was collected from the Potosi Mine, Santa Eulalia District, Mun. de Aquilies Serdan, Chiluahua, Mexico.

There are nice brassy crystals scattered on the specimen.  width FOV ~3.7 cm.

Photomicrograph of pyrrhotite crystals although light reflection does not allow for the brassy color to come through. Crystals are tabular in cross section but hexagonal when viewed down the C axis (as these are).  Width FOV ~1.2 cm.

Photomicrograph calcite crystals.  Width FOV ~1.2 cm.

Photomicrograph shiny black sphalerite crystals along with pyrrhotite and calcite .  Width FOV ~ 1.2 cm.

A second specimen is not a rare or uncommon mineral but is a new specimen (for me) from a favorite locality:  molybdenite (molybdenum sulfide: MoS₂) from the California Mine near Mt. Antero in Chaffee County, Colorado. The Mt. Antero gem mines (aquamarine mostly) were among the first high altitude localities that I explored upon moving to Colorado in 2006.  The geology of Mt. Antero/Mt. White has been described in numerous publications, the most comprehensive being Mark Jacobson’s book entitled Antero Aquamarines (1993).  In general, Mt. Antero/Mt. White is underlain by a rock unit termed the Mt. Antero Granite.  McIntosh and Chapin (2004) have assigned a date of 29.6 million years to the granite, or mid-Oligocene in age. Sharp (1976) described the granite as chiefly pinkish-orange, medium grained;… youngest of the plutons (intrusive igneous rocks) in the vicinity of Mt. Antero.  Miarolitic cavities (crystal lined cavities often containing unusual minerals) are common and are often filled with…beryl (including aquamarine), phenakite, and smoky quartz.

A flat plate-like matrix of beryl measuring ~5.7 cm. maximum width, and coated on both sides by bright flaky silver molybdenite crystals.  BTW, I cannot remove the photo of this specimen from the pyrrhoite photos--another Blogger quirk!

Photomicrograph from above specimen showing flaky crystals.  Width FOV ~1.0 cm.

My early trips to Mt. Antero were accessed by walking (twice) up the “Mt. Antero Road” through Baldwin Gulch off Chalk Creek Road west of Nathrop.  This is the major road that almost all rockhounds bounce and bump up. My initial walking treks were due to the fact that I wanted to summit (fairly) Mt. Antero at 14,276. Since the California Mine is a couple of miles southwest of the mountain on the flank of Carbonate Mountain at an elevation of ~12,500 feet, I decided one day (before several joint replacements) that a nice hike was in order and trudged up the Browns Creek Trail starting off US 285 south of Nathrop. 

The location of the California Mine is sort of obscured in the large talus slope on the mountain and an adit has been blasted shut. In 1953 Adams noted that “molybdenite occurs sparsely in small veinlets in the massive quartz outcrop of the vein…and is concentrated along surfaces that presumably represent the walls of open channelways or vugs. Away from such surfaces, it is in isolated flakes that in many places project into small voids between beryl and quartz crystals.”

I really did not find much of interest on the hike (except beauty and tired legs after a 12 mile in and out) and needed to retreat to a lower elevation as a summer monsoon storm was blowing in.  I do not enjoy electrical storms and quickly left the area never to return.  As best that I can tell, the California Mine had beryllium production from the beryl; however, I could not locate production figures.  MinDat also reported the presence of molybdenum and tungsten but again no production figures fell into my hands.  In fact, I am uncertain as to which mineral contained the tungsten.

Therefore, I was happy to locate the specimen shown below.  It originally came from the collection of coloradominerals.com, the owner/collector unknown since the domain site is now for sale.

Radiating aggregates of prismatic "soft" violet crystals of creedite from the Henderson molybdenite mine.Width FOV ~6.1 cm.

  

 Photomicrograph of a section from above specimen.  Width FOV ~1.4 cm.

A third specimen I acquired at Woodland Park is again a mineral that is not uncommon but certainly rather rare in Colorado. In a Posting on July 10, 2016, I described a specimen of creedite [Ca₃SO₄Al₂F₈(OH)₂-2H₂0], a hydroxyhalide mineral (minerals with a Halide Group anion—chlorine, fluorine, bromine, iodine--- plus the hydroxide radical) from the Cressen Pit at Cripple Creek (the famous gold mine).  Although the mineral creedite had been named (1916) from a locality in the San Juan Mountains near the community of Creed, it was not until 2001 that the second Colorado locality was recorded from the Cresson Pit.  And finally, in 2007, a third locality was reported from the Henderson molybdenum mine near Climax.  The Woodland Park show was the first time I had seen a specimen from this latter locality for sale so I “nabbed it.”

The final specimen brought back from Woodland Park is actually one that was not in my vocabulary (not a hard task to accomplish)---chondrodite (not to be confused with chondrite, stony meteorites) . As a softrocker I was totally unfamiliar with this metamorphic mineral, but it was cheap at four bucks and had some nice gemmy crystals.  Chondrodite is a somewhat rare neosilicate mineral [(Mg,Fe)₅(SiO₄)₂(F,OH,)₂] and is formed in a contact metamorphic environment, usually where hydrothermal solutions (created by heat from an intrusion) comes in contact with carbonate rocks (limestone or dolomite ormaybe even carbonatite) and where fluorine has been introduced by the fluids.  Most crystals of chondrodite are yellow, orange, red, red-orange, brown, red brown and occur as individuals or masses in remnants or the original carbonate, usually calcite or marble.  Changes in color intensity in the crystals is common.  Crystals are brittle and are easily fractured in a conchoidal manner.  Chondrodite is fairly hard at ~6.0-6.5 (Mohs), has a vitreous to greasy luster and a yellow to yellow-gray streak. It is transparent to translucent.  Some red crystals are quite gemmy and have been faceted.  In addition, a few crystals fluoresce an orange (SW) to yellow orange (LW).

 Crystals of chondrodite in a matrix of rhombohedral calcite.  Width FOV ~7.0 cm.

Photomicrograph of chondrodite crystals showing changes in color intensity.  Matrix of rhombohedral calcite.

In the United States the best specimens of chondrodite seem to be associated with intrusive rocks in New York and New Jersey, especially the Tilly Foster Mine located near Brewster, Town of Southeast, Putnam County, New York.  The mine was active from 1843 until 1897 with peak iron production in the 1870s, mainly from magnetite.  MinDat lists 120 minerals and stated the mine “is famous for its excellent brucite, chondrodite, clinochlore, titanite, and magnetite crystals and antigorite or lizardite (and other species) pseudomorphs after a wide variety of minerals.” 

REFERENCES CITED

Adams,  J.W., 1953, Beryllium deposits of the Mt. Antero Region, Chaffee County, Colorado: U.S. Geological Survey Bulletin 982-d.

Jacobson, M.L., 1993, Antero aquamarines: Minerals from the Mt. Antero-White Mountain Region, Chaffee County, Colorado: L R Ream Publishing.

McIntosh, W.C. and C.E. Chapin, 2004, Geochronology of Central Colorado Volcanic Fields: New Mexico Bureau of Mines and Mineral Resources.

Sharp, W.N., 1976, Geologic Map and Details of the Beryllium and Molybdenum Occurrences, Mount Antero, Chaffee County, Colorado. U.S. Geological Survey Misc. Field Studies Map MF-810.

If you want to see a little Woodstock live see if this will load:

 https://www.bing.com/videos/search?q=woodstock+live+videos&view=detail&mid=6DF53882817174785EFF6DF53882817174785EFF&FORM=VIRE

 

 

GOETHITE FROM THE PIKES PEAK BATHOLITH

The hardest thing to see is what is in front of your eyes.

In my long-ago undergraduate days in western Kansas students commonly worked deciphering the stratigraphy of the Cretaceous Dakota and/or Kiowa  formations.  If you did not want a project in the limestones or chalk beds, then the Dakota/Kiowa was about the only possibility within close driving distance.  In fact, my senior project was tying to map crossbeds in the Dakota and describing some sections.  I remember the rock colors of the Dakota were mostly red or orange (or so it seems).  We usually described the non-quartz and -calcite visible minerals as iron oxide or limonite and moved on from there. 

 

These large concretions (~10-12 feet) have eroded from the Dakota (maybe Kiowa) in Ottawa County, Kansas at Rock City.

As life progressed, I simply thought all red or orange “stuff” in these sandstones was limonite or some such iron oxide—who cared about trivialities?  

A piece of Dakota sandstone (~ 5 inches width) composed of microscopic quartz crystals/fragments cemented by calcite but with much iron oxide/hydroxide filling voids between the crystals, and coating the surface.  What do I call it--"limonite" or goethite or iron oxide/hydroxide?

Only later in life when my first teaching assignment included Sedimentary Geology did I “start to care,” at least a little!  BTW, teaching sedimentary geology was a joy since originally, I was assigned Structural Geology, a course that was not one of my strong points ( have you ever tried working with, and understanding, stereonets). 

A stereonet is a powerful method for displaying and manipulating the 3-dimensional geometry of lines and planes (www.sciencedirect.com)--or so they say, not so much for me!

Along with Sedimentary Geology I labored big time in Ground Water Resources in Western Kansas (I had never taken any sort of a ground water course), Invertebrate Paleontology, and Intro to Geology.  Yep, four different course preps for a kid who was trying to finish his Ph.D. dissertation and was soon to be a new father.  Spring semester was about the same with Historical Geology, Intro to Geology, Field Methods, and something else.  I finished the first good draft of my dissertation on a dark midnight in mid-February and my son was born the next day.  I have trouble, even today, remembering much of that first academic year, 1970-71, except the pay was $9000 for the academic year and no commitment for a second year.  However, things were going my way when a new tenure-track contract came in mid-May just as the three of us were heading to Dinosaur National Monument where I had a summer position.  Life was good and I did graduate that summer (although the Park Service would not let me miss a day to attend graduation in Salt Lake City).  After that hectic year I resumed remembering “things.”  

The reason my memory was recently jogged about iron oxide minerals is that Mr. Rockhounding the Rockies (rockhoundingkw.blogspot.com), one of the premier collectors of minerals from the Pikes Peak Batholith (age around 1.08 Ga) gifted me an absolutely gorgeous specimen of goethite, an iron oxide-hydroxide [FeO(OH)].  It reminded me, again, that not all iron oxides/hydroxides look like rust, appear as a coating of clay (as in limonite), attract a magnet (magnetite), are a critical ore of iron (hematite), nor do they all come from sedimentary rocks.

Goethite collected from rocks of the Pikes Peak Batholith near Lake George. Width FOV ~5.6 cm.  As with many dark, metallic luster, minerals photography is difficult with my equipment.  The specimen is much more attractive than depicted in the photo.

Photomicrograph of a 1.0 cm. width FOV section of above.  Individual prismatic crystals are east to observe.

In our basic chemistry/physical geology courses we learned that iron occurs in two different oxidation states: 1) ferrous iron has a plus 2 charge (written as Fe⁺⁺ or Iron II ) and needs to share two electrons with oxygen to form a neutral ion; 2) ferric iron has a plus 3 charge (written as Fe⁺⁺⁺ or Iron III) and needs to share three electrons with oxygen to form a neutral ion.  Ferric iron is more stable than ferrous iron, the latter then commonly is oxidized (adds more oxygen) and becomes ferric iron.

Ferrous oxide is rare as a mineral due to its lack of stability and about the only mineral is wustite, a rare oxide usually found in meteorites and man-made slag from smelters.  The cation iron has a ++ oxidation state (plus 2) and the anion oxygen has a - - (minus 2) oxidation charge so they balance out: one iron (++) combined with one oxygen (- -) = FeO.

The major ferric iron mineral is hematite, Fe₂O₃.  Here you can see two units of iron (charge of +++) X 2 = 6 combine with three oxygen units (charge of - -) X 3 = 6  or +++ X 2 irons = 6 and - - X 3 = 6 oxygens.  So, it balances.  

There also is a major iron oxide mineral termed magnetite, Fe₃O₄  that appears not to balance!  However, magnetite is actually composed of both ferric and ferrous iron and should be written as: FeO-Fe₂O₃, one part of each (one unit of ++iron (2) and two units of +++ iron (6) = 8.  One unit of - - oxygen (2) and three units of - - oxygen (6) = 8.  Wow, it balances.

Iron minerals become even more complicated when one considers the iron hydroxides where the OH ion with a charge - - (minus 2) combines with iron.  As far as I can tell, ferrous (Iron II) can combine with a hydroxide ion, but only as a solution in the lab: Fe⁺⁺(OH)_2. One iron ++ and two hydroxides - .  So, one iron ++(2) combines with two hydroxides - -(2) and it balances.

Ferric (+++ or Iron 3) iron may combine with hydroxide to form a really rare and complex mineral called bernalite [Fe(OH)₃]: One Fe+++ (3) combines with three hydroxides each with a charge of minus 1– to equal 3, and it balances.

Another major group of iron and oxygen minerals are the Ferric (Iron III) oxide-hydroxides: ferric iron plus the hydroxide ion plus oxygen.  The major mineral in this group is goethite, FeO(OH).  In goethite there is one unit of ferric iron with an oxidation state of +++ that combines with one oxygen (oxidation state of - -) and one hydroxide (oxidation state of -).  So, three of iron equals the two of oxygen plus the one of hydroxide, 3 = 3.

In reality, there are at least three named polymorphs of goethite---exact same chemical formula but crystallizing in different crystal systems: akageneite, lepidocrocite and feroxyhyte.

But, what about limonite, that rusty clay or black streak or “ironstone” or whatever that is common in the orange or red Dakota Sandstone of my youth.  Is the mineral ferric or ferrous iron and is it an oxide, or a hydroxide or an oxide-hydroxide? It turns out that limonite is not even a mineral [often written as Fe+³O(OH)-nH₂O] but a combination of several “real” minerals---goethite, lepidocrocite, akaganeite, maghemite, hematite, pitticite, and “jarosite group” minerals and the term is used “for unidentified massive hydroxides and oxides of iron, with no visible crystals, and a yellow-brown streak” (MinDat.org).  Commonly, limonite is composed of goethite.

I am still not certain that I can identify goethite from limonite in many orange to red sedimentary rocks since both have similar colors (red, reddish brown, yellow brown, brownish black), similar hardness (5.0-5.5 or 4.5-5.0 in limonite[Mohs]), dull to metallic to adamantine luster, and a yellowish brown to orange-yellow streak, and often massive.  However, the goethite from the rocks of the Pikes Peak Batholith is different in that it often forms spectacular crystals.

The Pike Peaks goethite is composed of slender, flattened crystals that are elongated along the C-Axis, vertically striated, and exhibit a  metallic luster.  They form “clumps” of radiating crystals and appear to be black or brownish black in color.  However, the streak is brown to brownish yellow to yellow orange.  The crystals are secondary in nature and are derived by weathering (an oxidizing environment) of many different iron-bearing minerals.  Mr. Rockhounding the Rockies has collected his goethite specimens from the same cavities that produce amazonite and smoky quartz (see his web site for many photos).

To learn more about goethite, and especially Goethe, check out my Blog posting on April 23, 2012: Goethite, Goethe, and Kaninchen.

And finally, words of advice from Johann Wolfgang von Goethe (1749-1832): Every day we should hear at least one little song, read one good poem, see one exquisite picture, and, if possible, speak a few sensible words.

The hardest thing to see is what is in front of your eyes. See top of article. Johann Wolfgang von Goethe