CAMP BIRD, COLORADO, SPHALERITE

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.

REFERENCES CITED

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 22^nd edition of the Manual of Mineral Science: John Wiley & Sons, Inc., New York.

THE TRIVIA

'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