Tuesday, June 28, 2016


The other day I was rummaging through a drawer of specimens from Colorado during a period of, for want of better terms, reorganization, cleaning and relabeling, when I came upon a nice specimen from the Ouray area in the San Juan Mountains.  In the 1970s I was spending much/most of the summers collecting and supervising student projects/theses in various parts of Utah—mapping, collecting fossils, stratigraphic studies.  However, I always tried to take a break on the way back to my teaching position in Kansas by camping and hiking and fishing in Colorado.  I mean if you are going to drive from Utah to Kansas one might as well spend some R & R in the Colorado mountains!  Several times we camped down in the San Juan Mountains near Ouray or Telluride and I was able to wander around and check out some of the mine tailings and dumps.  My momma didn’t raise no fools so I did not venture anywhere close to a shaft or mine opening.  Besides my momma’s warnings, I have a bad case of claustrophobia!  
One of my favorite back country roads was/is the Ouray County Road 361 known as the Camp Bird Road or the Yankee Basin Road exiting US 550 just south of Ouray and heading to the high country.  The road eventually dead ends at about 12,500 feet, OR branches out heading over Imogene Pass (~13,000 feet) to the area around Telluride.  I am not much for traversing narrow, four-wheel drive, high mountain passes so have passed on Imogene (and most others).  The Camp Bird Road itself is quite narrow with “drop offs” of several hundred feet.  Forty years ago the road remained relatively unknown to “tourists” but today it is often crowded (especially on summer weekends) with fours-wheel and OHV enthusiasts, as well as numerous Clark Griswolds attempting the trip in their family sedans.  Sometimes those latter journeys are a “sight to behold.” Even in winter the road is “busy” with ice climbers, cross country skiers, snowshoers and other snow/cold weather enthusiasts.
Hanging Rock along the Camp Bird Road to Yankee Basin.
If the Camp Bird Road is a dramatic drive with fantastic views, then Yankee Boy Basin is sort of a spiritual experience.  It is a high altitude alpine basin with views and access to spectacular scenic peaks such as Mount Sneffels (14,150), Gilpin Peak (13,694), Teakettle Mountain (13,825), Potosi Peak (13,786) and numerous others.  One of my goals in life when moving to Colorado was to attempt a summit of Sneffels; however, increasing age with new hips and knees, and children who insisted that I locate a hiking partner, limited my 14ers to several in northern Colorado.  I suppose those days are over but I have the memories and feel blessed that Elbert and several others succumbed to my persistence.
Lots of high country with peaks composed of volcanic rocks.
A trip to Yankee Boy Basin also exposes the traveler to numerous abandoned mines, mills and dumps.  Some areas are on private land, some on federal USFS land, and some are under claim—a hodgepodge of ownership that is tough to decipher.  The best plan, if you want to examine the tailings etc., is to check with the local USFS office about ownership.  But again, back in the 1970s it was easier to just walk around and explore. 
Perhaps the most photographed mining activity is the area around the Atlas Mill and Mine (~.75 miles past the Imogene pass turnoff).  It is tough to locate much information about the Atlas Mine except it is several hundred feet above the modern Revenue Mine, a climb that I did not want to make.  It seemed active in the late 1800s and I presume was one of the numerous sulfide mines that dot the area.  But, remains of the Atlas Mill that processed the Mine ore are quite visible near the Camp Bird Road adjacent to Sneffels Creek.  Several years ago there was an adjacent campground; however, during my last visit the site was closed as an avalanche (2008) had destroyed the area.  The former town of Sneffels occupied the area around the Atlas Mill.  The Revenue Mine may still be in business as a couple of miners were killed in an accident about three years ago.

Abandoned mines and tailings are common along the Camp Bird Road.
The photogenic remains of the Atlas Mill across Sneffels Creek and along the Camp Bird Road. The Atlas Mine was several hundred feet above the Mill.
One of the more famous mines in the area was/is the Camp Bird Mine located near the former community of Camp Bird.  Today the mine is on private property and it appears, at least to me, that much of the area has been reclaimed, or at least protected from further damaging the environment.  The local newspaper in Ouray had noted, back in about 2013, that the mine was being processed for reopening.  However, a local person from Ouray told me that those rumors have circulated since the mine closing in 1990.  MinDat.org states the Camp Bird Mine is: “a former Au [gold]-Zn [zinc]-Ag [silver]-Pb [lead]-Cu [copper] mine…Discovered by Thomas F. Walsh in 1896… Mineralization is a polymetallic replacement deposit. The main ore body is the Camp Bird vein, with replacement ore bodies on three other veins. The ore body…is a tabular, fissure vein replacement body. The primary mode of origin is hydrothermal. Secondary mode was lithology…Local rocks include pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates. Workings include extensive underground openings with a length of 7,200 meters and an overall depth of 248 meters…Produced about 1.5 million Troy ounces of Au [gold] to 1990. Also produced 4 million Troy ounces of Ag [silver].  The Colorado School of Mines (2016) noted that: “ the Camp Bird vein – a major control structure for the mine – was formed as a result of the subsidence of the nearby Silverton Caldera. The vein is located about three miles northwest of this caldera. The vein out crops near the head of Imogene Basin at an elevation of 11,800 feet. Ore shoots along the Camp Bird vein account for almost all the gold production from the mine.  [The emplacement of the epithermal sulfide ores was probably around the mid-Miocene]

Throughout the 90+ years of mining operations at Camp Bird, three different types of epithermal ore deposits have been mined:
1) Gold-quartz-base-metal ore shoots.
2) Silver and base metal-bearing quartz veins.
3) Lead-copper-zinc replacement ore bodies (ROBs).

The primary ore minerals of the Camp Bird vein are native gold, galena, sphalerite, chalcopyrite, and tetrahedrite. The main gangue minerals are quartz, pyrite, and calcite. Other prominent minerals include: epidote, fluorite, gypsum, hematite, rhodonite, and scheelite.”

The specimen that I picked up a long time ago is a nice rock with beautiful crystals of sphalerite (ZnS) along with a few crystals of galena (PbS).  Sphalerite is a rather common sulfide mineral and is the major ore of zinc.  It is in the Isomorphic Crystal System but instead of producing just simple cubes it also forms tetrahedrons and dodecahedrons and all forms are commonly twinned, intermixed and highly complex; at times it occurs as microcrystalline, or botryoidal and compact masses.   One of the most distinguishing features is the luster, usually resinous to submetallic to vitreous.  On larger crystals the cleavage is quite noticeable; however, the granular masses do not cleave. Crystals are translucent to transparent to opaque and some gemmy material has been faceted; however, these pieces are for collectors only as the perfect cleavage and the mineral softness (3.5-4.0 Mohs) does not allow for jewelry use.  The color of sphalerite varies with composition.  The more “pure” Zn~67%S~33% is usually a pale yellow to yellow green to orange to red; however, iron is a common constituent and replaces some of the zinc.  With increasing iron content, the darker the crystals become until they are quite dark and opaque. As I understand the situation the amount of iron in sphalerite may be an indication of the formation temperature (Klein, 2002).  Trace amounts of manganese can also darken the crystals.  A sphalerite dimorph, wurtzite [(Zn,Fe)S], belongs to the Hexagonal Crystal System. 
Complexly twinned and distorted dark brown sphalerite crystals and smaller gemmy yellow crystals along with three tarnished, gun-metal gray weirdly twinned galena crystals (G). Width of specimen ~6.5 cm. See photomicrographs below.

Above three photomicrographs show the nice dark brown crystals along with much smaller gemmy, translucent yellow to amber crystals.  The dark brown crystals range around 3-6 mm in width.  Several of the larger crystals are twinned or distorted and/or striated.  The amber to yellow crystals seem not to show twinning.
The specimen that I have from the Camp Bird Mine has a mixture of complexly twinned, fairly large, almost black, subvitreous crystals intermixed with gemmy, small, pale yellow crystals.  However, the large dark crystals may be scratched with steel to reveal the underlying yellow-green color.  And some crystals contain both opaque and transparent/translucent areas.  Eckel and others (1997) noted that "in the replacement bodies of the Camp Bird mine, sphalerite often is the predominant ore mineral, occurring in a translucent green variety, and a dark, nearly opaque variety..  many excellent crystallized specimens are known from the Orphan replacement orebody."  Intermixed are some really complexly twinned, tarnished gun-metal, galena (PbS) crystals.  It is a nice specimen and is completely different looking than my specimens from the Tri State Mining area in southeast Kansas.
Small penetration twin on larger galena crystal. Width of larger crystal ~4 mm.

The above two photomicrographs is a galena crystals with "strange" (at least to me) twinning or a center cube with epitaxial growth along all sides.  It is tough for my camera to pick up the shape but there is a center cube with twins/growths tilted up along each edge forming sort of a box that still needs some folding. Total width about 4 mm.


Colorado School of Mines, 2008, Mining Stories of the Colorado School of Mines Geology Museum: www.facebook.com/likecsmmuseum/posts/1635501270070589

Eckel, E.B. and others, 1997, Minerals of Colorado: Friends of Mineralogy – Colorado Chapter and Fulcrum Publishing, Golden, Colorado.

Klein, C. (after J.D. Dana with continued contributions of C.S. Hurlbut,Jr.), 2002, the 22nd edition of the Manual of Mineral Science: John Wiley & Sons, Inc., New York.


'Way out in Colorado
In the Camp Bird Mine
Down deep in the darkness
On level nine
Where the water trickles
An' your blood runs cold
There's a lonesome miner
Still lookin' for gold

CAMP BIRD MINE, as sang by C.W. McCall (he of Convoy (1975) and Rubber Ducky (1976) fame), and the former Mayor of Ouray.

Thomas Walsh discovered (1896) and operated the Camp Bird Mine until selling it in 1902 for a gazillion dollars and moving to Washington, D.C.  His heiress daughter, Evalyn Walsh McLean, purchased one of the most famous gemstones in the world, the Hope Diamond, a 45.52-carat deep-blue diamond.  In 1949 the estate of Ms. Walsh sold her jewelry to the New York gemstone merchant Harry Winston.  In 1858 Mr. Winston donated the Hope Diamond to the National Museum of Natural History (Smithsonian) to

help start a national Gem Collection.  And it all started with a little gold and sphalerite found in the high country of the San Juan Mountains.
See the Posting on 1—11-16 Stromeyerite, Silver and Kevin Bacon

Sphalerite and gold
were mined at Camp Bird and allowed owner
Thomas Walsh
to become very wealthy and bequeath many millions to his daughter
Evalyn Walsh McLean
who was then able to purchase the famous Hope Diamond that later landed in the
Smithsonian Institution
and was seen in the
National Gem Collection
display by visitor
Kevin Bacon  


Wednesday, June 22, 2016


As noted in the previous Post, the CSMS annual Show was a huge success with a large number of vendors, great display cases, and numerous satisfied visitors.  After visiting Tucson in February, and locating several blue-colored minerals (Show theme was Shades of Blue), I was now on the lookout at the CSMS show for additional blue minerals that were out of my price range in Arizona.  Much to my surprise I was able to pick up small specimens of boleite and diaboleite; both minerals are complex halides rather uncommon in the rock record.

Boleite [KPb26Ag9Cu24(OH)48Cl62] has been known since the early 1890s but was not well understood until the late 20th century with the advent of sophisticated instrumentation.  The discovery locality, the Boleo Copper District located in Baja California Sur, Mexico, near the town of Santa Rosalia, has been the site of major sulfide mining (open pit until the 1980s) and at one time (at least in the 1950s) was the second largest producer of copper in Mexico (Wilson and Rocha, 1955). Underground mining started in 2012 with the first production in 2014 and I presume mining is still active.   As best I can decipher, the copper deposits are in an uplifted belt of Neogene (Miocene or Pliocene) rocks within the El Boleo Formation (deltaic and near-shore marine claystone-siltstone-sandstone beds).  The major sulfide ore minerals are chalcocite (Cu2S) accompanied by chalcopyrite (CuFeS2), bornite (Cu5FeS4), covellite (CuS), and native copper (Cu).  The oxidized zone (above the sulfide deposits) has a large variety of copper oxides, copper carbonates, copper silicates, manganese oxides, and rare halide minerals such as boleite, pseudoboleite, and cumengite.  The Boleo deposits are the type locality of the latter three halide minerals. The productive ore contains rather large amounts of copper, manganese, zinc, cobalt, lead, and silver; however, few minerals except copper were produced in commercial quantities.  Evidently the hydrothermal solutions traveling through the underlying Comondu volcanics (Miocene?) from even older (?Cretaceous) intrusive igneous rocks ( a quartz monzonite) carried metallic elements upwards in fractures and faults before depositing the sulfide ores in sedimentary rocks and sediments of the El Boleo Formation.  (above geological information from Wilson and Rocha, 1955).  The mineral deposits at Boleo are termed epigenetic since they formed after deposition of the host rocks.  Syngenetic would indicate deposition of mineral deposits simultaneously with deposition of the host rocks

The Boleo ores are interesting in that they are a Manto ore deposit.  These deposits are usually polymetallic in nature and form sheet-like bodies along bedding planes of sedimentary rocks.  The hydrothermal, metal-bearing solutions circulating off nearby igneous rocks (usually intrusive) supply the ore minerals. The types of primary sulfide minerals vary with the composition of the hydrothermal solutions.  Evidently the hydrothermal solutions at Boleo were rich in lead, copper, silver and a few other metals.  Oxidation and weathering of some sulfides allowed for the formation of the many colorful oxides, chlorides and carbonates.  MinDat lists 68 different minerals collected from the Boleo deposits.

So, the metals in the hydrothermal solutions are cations, positively charged molecules with more protons than electrons.  The metallic elements have a neutral charge but they emit electrons and lose their neutrality (and become  cations).  Chloride (Cl) is a negatively charged (more electrons than proton) anion (the anion of the neutrally charged element chlorine).  Cations, such as the lead, copper and silver in boleite are attracted to, and bond with, the negatively charged chloride anion. [KPb26Ag9Cu24(OH)48Cl62]---I understand that concept.  But my question is---what is the source of the chloride in boleite?  Was it in the original hydrothermal solution, or was it completely secondary?  My guess, and this really is above my pay grade, is the chloride came from the host marine rocks and not from the original hydrothermal solution. I say this since MinDat notes that boleite also forms, rarely, when smelter slags are immersed in, and leached by, seawater (contains NaCl).  Boy, where are my mineralogy/petrology/ore genesis friends?  Whatever, chloride reacted with the sulfides and like magic----boleite and other halides.

Well, the above paragraph took a couple or three hours to write and I am not certain the sentences are correct.  I blame this lack of understanding on: 1) college chemistry befuddled my 18-19-year-old mind; 2) my first year in college was paid for by a basketball scholarship and that aspect was foremost in my thoughts; and 3) after struggling through those confusing chemistry courses I switched to geology and paleontology and as the saying goes, “found my niche.”  Now 50+ years later I am trying to relearn some basic chemistry---lifelong learning at its best! But this learning is tough, about like when I tried to master the German language ten years ago.  Well, not really master it but just try for some basic understanding.  I sort of achieved that aspect since I could order dark beer (dunkles Bier), bread (brot), sausage (wurst) and especially pig knuckles (schweinehaxen), as well as read the train schedules.  What more does one need in Germany?  I am still working on the chemistry aspect!

OK, so boleite is one of those uncommon hydroxyhalides (chlorine is cataloged into the Halide Group of elements) and the chemical formula [KPb26Ag9Cu24(OH)48Cl62] shows the presence of a hydroxide ion (OH). Crystals have a beautiful indigo to prussian blue color; however, the color often appears much darker when examining a complete crystal in reflected light. It has a vitreous to pearly luster and is fairly soft (3.0-3.5 Mohs).  Thin pieces are transparent but larger crystal pieces appear opaque or at least translucent.  The powered form, streak, is a greenish-blue color.  Boleite belongs to the Isomorphic Crystal System and crystals are cubes although they commonly are twinned (Interpenetration Twinning) or have epitaxial pseudoboleite [Pb31Cu24Cl62(OH)48] or cumengite [Pb21Cu20Cl42(OH)40-6H2O]. 
Photomicrograph of boleite cube with lower left corner chipped.  Width/length of cube ~ 5 mm.
Photomicrograph of boleite cube showing smaller penetration cube.  Width/length of large cube is ~3 mm.
Photomicrograph of boleite cube (upper) attached to a second boleite cube (B) surrounded by epitaxial pseudoboleite (P). Abdul-Samad and others (1981) stated "since pseudoboleite is never found without boleite upon which it is observed to geow epitaxially (Winchell, Ohio State University thesis, 1963), it is clear that boleite must form metastably prior to any pseudoboleite deposition."  Width of lower B-P section ~ 2.9 mm.
Photomicrograph of boleite cube (B) with epitaxial pseudoboleite. Width of photo ~4 mm.

Most boleite specimens on the market today come from the Boleo District and many/most seem to be floaters; crystals scattered over a matrix are rare and expensive.  According to one prospector/vendor I talked to in Tucson, boleite crystals of any kind are getting rather scarce.  In the U.S. the best-known boleite crystals are from the Mammoth-St. Anthony mine northeast of Tucson.

Speaking of Mammoth-St. Anthony, the specimen of diaboleite purchased at the Show is from this famous Arizona mine.  Diaboleite is also a hydroxyhalide [Pb2CuCl2(OH)4] with lead and copper as the cations along with a chloride anion.  It forms in a similar environment as boleite, in the secondary zone of copper-lead deposits, and at times is found in association with boleite.  Diaboleite is also blue in color that seems not as intense (the prussian blue) as boleite.  It is quite soft (2.5 Mohs), crystals have a vitreous luster and are more transparent than boleite.  The streak is about the same as boleite but seems a little greener.  The major difference between the two minerals is that diaboleite belongs to the Tetragonal Crystal System and produces crystals that are tabular although specimens are often a mixture of nice crystals and very tiny granular crystals packed together.

So again the question about the chloride ions!  Humphreys and others (1980) noted that “halide salts are generally soluble in water, which explains why halide minerals of the transition elements are usually absent from the vicinity of oxidizing orebodies. In such an environment low pH values also tend to facilitate the solution of most species. Nevertheless, many halide minerals are known and occur in considerable quantities at some localities. Two groups of halide minerals containing Cu(II) and Pb(II) are outstanding in their complexity and rarity. These are the boleite group…and diaboleite [+others]… These…minerals are thus apparently confined to systems where the availability of chloride ions is very high.”  They furthermore observed these oxyhalides and hydroxyhalides can only form from aqueous solutions as secondary minerals.  As to why specific oxyhalides or hydroxyhalide minerals form, Humphry and others (1980) and Ardul-Samad and others (1981) conducted a number of solution studies and constructed Stability Field Diagrams that indicate the parameters (especially pH) needed for deposition of these specific copper chloride minerals.  As to the origin of the chloride, Ardul-Samad and others (1982) stated that the minerals occurring at Mammoth-St. Anthony are “an extremely complex assemblage in the oxidized zone of a base-metal orebody…a diverse and complicated inorganic chemistry must have been responsible for the formation of the compounds…”  I presume this latter statement could also apply to the Boleo Copper District.

In my discussion of boleite, I suggested that perhaps the chloride in the oxidized zone came from the host marine rocks/sediments but that was sort of a guess from a non-mineralogist!  I am still looking for an answer; however, Frost and others (2003) noted that “several chloride minerals of the base metals is known from oxidised zones, especially those located in arid areas, or those which are associated with saline ground waters.”   I presume, but again a guess, that the chloride in the “saline ground waters” came from ground water percolating through the host rocks/sediments!


Abdul-Samad, F., D.A. Humphreys, J.H. Thomas, and P.A. Williams., 1981, Chemical studies on the stabilities of boleite and pseudoboleite: Mineralogical Magazine, v. 44. 

Abdul-Samad, F., J.H. Thomas, P.A. Williams, R.A. Bideaux and R.F. Symes, 1982, Mode of formation of some rare copper (II) and lead (II) minerals from aqueous solution, with particular reference to deposits at Tiger, Arizona: Transition Metallic Chemistry, v.7.

Frost, R., Martens, W. and P. Williams, 2003, Raman spectroscopy of the minerals boléite, cumengéite, diaboléite and phosgenite –implications for the analysis of cosmetics of antiquity: Mineralogical Magazine v. 61.

Humphreys, D.L., J.H. Thomas, P.A. Williams and R.F. Symes, 1980, The chemical stability of mendipite, diaboleite, chloroxiphite, and cumengite, and their relationships to other secondary lead(II) minerals: Mineralogical magazine, v. 43.

Wilson, I.F. and V.S. Rocha, 1955, Geology and mineral deposits of the Boleo copper district, Baja, California, Mexico: U.S. geological Survey Professional Paper 273.

Sprichst du Deutsch? Nicht wirklich. Gerade genug, um die Züge und um Essen zu fahren. Aber kein Kaninchen.

Haben Sie Chlorchemie zu verstehen? Nicht sehr gut, aber ich habe intelligente Freunde.

Das ist alles, Leute!
Courtesy of  picgifs.com