CRACKING ROCKS AT TEEPEE CANYON:AGATES

BISMARCK LAKE NEAR CUSTER, SOUTH DAKOTA-VIEW FROM THE CAMP SITE.

I have visited the Teepee Canyon agate area a couple of times in the last few years, but without much success.  On my initial visit I did not have the proper equipment and my undersized rock hammer was of little use.  I found a few agate fragments but certainly nothing to write home to momma about.  On my second visit I ran into a rain storm and the roads did not look very passable and I am somewhat terrified of lightening.  My momma did not raise no fools!

TEEPEE CANYON AGATES AT THE AMERICAN FEDERATION 2012 SHOW.

 But, I am persistent and in summer 2012 I was bound and determined to go back to the Canyon and pound on the rocks.  Teepee Canyon is located approximately18 miles west of Custer, South Dakota, about 2 miles west of Jewel Cave National Monument off U. S. 16.  As soon as travelers leave the Monument they should look to the west, up slope, and begin to spot piles of broken rocks, big pieces.  Sawmill Spring Road, (FS 456) leads off to the west and about a mile further West Teepee Canyon road takes off.  My best advice is to follow one of these roads/tracks and look for quarries where past prospectors have tried their luck.  The land is managed by the U.S. Forest Service and all previous claims have expired (as I understand it).  The gentleman in the local USFS office in Custer told me that only hand tools were allowed and to stay in the area of previous mining (I left the big fircrackers in the vehicle).  It is my understanding that after the fire of 2000 other agate producing areas external of the main Teepee Canyon site had been discovered.  I don’t know if these are claimed.  What I do know is that there are enough “big rocks” at Teepee Canyon to last me a lifetime!

THE DIGGINGS AT TEEPEE CANYON. 

 The agates are located in chert nodules housed within the lower Minnelusa Formation.  I suppose these nodules are the result of silica-rich meteoric waters circulating through the unit with resulting diagenesis producing the chert.  Why some nodules are agatized—I don’t have the slightest idea.  Just as I am uncertain how/why agates really form!  The formation of agates in several types of rocks is extremely complicated, even for the “experts”.

The Minnelusa sits on top of a widespread carbonate unit termed the Mississippian-age Madison Limestone, or the Pahasapa Limestone as it is generally known in South Dakota.  In the early part of the Pennsylvanian (younger than the Mississippian) the climate was warm and quite wet in the future South Dakota and a red soil developed on the Madison.  Later in the period marine waters returned and rocks of the Minnelusa were formed. The Minnelusa is an interesting rock unit composed of beds of sandstone, dolomite, and thick beds of anhydrite.  Braddock (1963) noted that dissolution of some of the anhydrite had caused numerous collapse structures and collapse breccias in the Black Hills.  Originally designated as Pennsylvanian in age, fossils in the Minnelusa indicate both a Pennsylvanian and Permian age.  I presume that since the agates seem to be in the lower part of the formation, they belong to the Pennsylvanian.  I was able to locate brachiopods in some of the beds at Teepee Canyon but am uncertain as to their exact age.

CHERT NODULES IN MINNELUSA FORMATION.

BRACHIOPODS IN MINNELUSA FORMATION.

The nodules at Teepee Canyon are composed of chert, often red to tan in color, and of various sizes.  Very few of these nodules are agatized so locating a good agate is “hard work”.  First of all, the enclosing carbonate matrix is mostly a fine-grained dolomite that is extremely hard and quite difficult to “break”; hence, the need for a large crack hammer, eye protection, heavy clothes, and preferably steel-toed boots.  Many prospectors/miners at Teepee Canyon have cut into the outcrop and removed “really large” pieces of dolomite to crack open.  I decided early on that sort of mining was not on my agenda and simply cracked open smaller pieces mined by others.  The nodules in the carbonate were quite numerous and it appeared, at least to me, that some of these would polish quite nicely.  But, I was after agates!  I found numerous smaller pieces, all fragments less than one-half inch long, but then—there it was, a real Teepee Canyon agate.  Now, it is nothing spectacular, perhaps 1.25 x 1.0 inches in size, but never-the-less it was mine, and it satisfied my yearning!  So, after about two and one-half hours of cracking rocks in a hot sun I decided to take my find and return to camp on beautiful Bismarck Lake by Custer State Park.

AGATE ROUGH COLLECTED SUMMER 2012.

RED SOIL DEVELOPED ON TOP OF MADISON FORMATION NEAR JEWEL CAVE NATIONAL MONUMENT.  SOIL FORMED IN A WET AND WARM CLIMATE.

 mike

REFERENCES CITED

Braddock, W.A., 1963, Geology of the Jewel Cave SW Quadrangle, Custer County, South Dakota: U.S. Geological Survey, Bulletin 1063 G.  

CROW PEAK: A POCKET LACCOLITH

A SMALL LACCOLITH NEAR SUNDANCE, WYOMING.

The Laramide-age Black Hills, the dominant landform in western South Dakota extending into Wyoming, is surrounded along the northern boundary by igneous intrusions.  The June 10, 2012,  blog posting described one of these intrusions near Sturgis, South Dakota, known as Bear Butte.  Near Sundance, Wyoming, there are a series of related, small Eocene laccoliths (an igneous mass intruding between layers of sedimentary rock and doming the overlying layers; at times the domed sedimentary rock is eroded away and igneous rock is exposed)  intruding through the Mesozoic rocks; all are easily visible from the highway--Sundance Mountain (5829 feet), Black Buttes, Inyan Kara Mountain (6368 feet), Missouri Buttes (5055 feet) and the Bear Lodge Mountains (~6600 feet).  A little further to the northwest of Sundance is the best known of the intrusions, Devils Tower (may not be part of a laccolith but some sort of an igneous intrusion; 5112 feet).

SECTION FROM MISSOURI BUTTES EASTWARD TO BELLE FOURCHE RIVER THROUGH DEVILS TOWER.  FROM USGS PROFESSIONAL PAPER 65, 1909.

INYAN KARA MOUNTAIN SOUTH OF SUNDANCE, WYOMING, A SACRED PLACE TO NATIVE AMERICANS.  THE PEAK WAS VISITED BY MEMBERS OF THE 1874 BLACKS HILLS EXPEDITION LEAD BY GEORGE ARMSTRONG CUSTER.  A SCIENTIST IN THE EXPEDITION (DONALDSON)  STATED THERE IS NO GRANITE OR OTHER PRIMARY ROCK IN THE MOUNTAIN, NEITHER BASALT OR TRAP. THE WHOLE IS AN IMMENSE UPHEAVAL OF NON-FOSSILIFEROUS, SEDIMENTARY, METAMORPHIC ROCK.  PHOTO AND QUOTE FROM WYOMING STATE HISTORIC PRESERVATION OFFICE.

OFFICE.

NORTHWEST-SOUTHEAST SECTION THROUGH INYAN KARA MOUNTAIN.  FROM USGS PROFESSIONAL PAPER 65, 1909.

I-90 then proceeds into South Dakota toward the city of Spearfish.  I have always enjoyed camping around, and visiting, this community for a number of reasons.  Spearfish Canyon leaves town and follows Spearfish Creek southwest toward Savoy and a summit.  A wonderful section of Paleozoic rocks are exposed along the route and the Creek offers some great fly fishing opportunities.  One can also locate the “final scene” from the movie, Dances with Wolves (http://dances-with-wolves.purzuit.com/video/LR4j8iWu-OI.html).  At this locality, up Forest Road 222 (west of Savoy), Wind in His Hair shouts from the cliff (Pahasapa Limestone of Mississippian age) as John Dunbar is leaving the tribe Shumanitutonka Ob Wachi!  Although I took exception to movie's rendition of Fort Hays (I lived there for 24 years), this final scene in the Black Hills was pretty spectacular!

CLIFF OF PAHASAPA LIMESTONE AT FINAL SCENE FROM DANCES WITH WOLVES.

 I also am fascinated by the area’s small laccoliths that just intrude and push up through the Paleozoic rocks.  I am far from a petrologist or structural geologist and really do not understand all of the emplacement mechanisms except that somehow they seem related to the Laramide Orogeny; however, they are enjoyable to observe and climb—Crow Peak (5760 feet), Citadel Rock (5410 feet), Ragged Top (6220 feet) and Spearfish Peak (5764 feet).  Most have a quartz latite porphyry (plagioclase phenocrysts in a fine groundmass of orthoclase feldspar; Lisenbee and others, 2007) in the center surrounded by the Cambrian-Ordovician Deadwood Formation (sandstone), some lower Paleozoic thin carbonates and the massive, cliff-forming Mississippian Pahasapa Limestone.  Most structures are rather circular in nature and are generally “off the beaten path”.  They evidently are Eocene in age and related to the other small intrusions.  Elkhorn Mountain further east down I-70 is an intrusion where the igneous core has not been exposed and additional small laccoliths are located south of Sturgis.

In the Spearfish area I am especially enamored with Crow Peak.  There is a beautiful “back road” leading out to the summit trail (1560 feet elevation gain) and it appears a fall drive would display some fantastic colors.  I thank my guide Junior Geologist for introducing me to both the peak and the aptly named Crow Peak Brewing Company.
mike

CROW PEAK, AN EOCENE LACCOLITH NEAR SPEARFISH.

 

SECTION THROUGH CROW PEAK.  FROM USGS PROFESSIONAL PAPER 65, 1909.

GEOLOGIC MAP OF CROW PEAK SHOWING CIRCULAR NATURE OF LACCOLITH AND IGNEOUS ROCKS IN THE CORE.  FROM LISENBEE AND OTHERS, 2007.

REFERENCES CITED

Lisenbee, A. L., J. A. Redden, and M. D. Fahrenbach, 2007, Geologic Map of the Maurice Quadrangle, South Dakota: South Dakota Geological Survey, Vermillion.      

WOW--SOUTH DAKOTA ARTESIAN WELL

ARTESIAN WELL AT WOONSOCKET, SD, SUMMER 2012.  LAKE PRIOR SURROUNDS WELL.

 Woonsocket, South Dakota, is a small community in the east-central part of the state along SD 34, a highway I recently traveled from Pierre to Pipestone, Minnesota.  I always enjoy getting off the Interstate system and exploring “Blue Highways” (see recent issues of the CSMS Pick & Pack for many other Blue Highways stories).  At any rate, it was a very hot and windy summer afternoon when I arrived in Woonsocket looking to purchase some cold water (in case readers are wondering about the moniker, the city was named for a town in Rhode Island).  When entering the city I first thought that a large fire hydrant had broken as a giant plume of water was thrusting into the air (several tens of feet).  But upon closer examination I saw that the water was coming back down into a quite scenic small city lake.  What in the world—is this a fountain of some sort?  But then as I grabbed the cold water and guzzled it down, the back recesses of my mind begin to function again and something popped up about artesian waters. I remembered from my student time in South Dakota that the central and eastern part of the state had numerous artesian or free flowing wells. The water seemed to originate in the Black Hills and move down slope to the east under confined pressure.  However, over the resulting years, many/most of these wells had lost their head (pressure) and no longer flowed to the surface or at least did not spout into the air.

ARTESIAN WELL AT WOONSOCKET, SD, CA. 1900.  THE SPOUT IS NEARLY 100 FEET TALL.  FROM U.S. GEOLOGICAL SURVEY PHOTO ARCHIVE.

 During one summer in 1966 I was stationed and working at Chamberlain where I-90 crosses the Missouri River.  As sort of a history nut I remember reading that before the Corps of Engineers dammed the River near Fort Randall (and created Lake Francis Case extending up river past Chamberlain), a number of wells were drilled into the artesian system along the river lowlands.  There is a picture somewhere I don’t remember showing this one fantastic well free-flowing ?4000 GPM and helping to run a small mill of some sort.  I presume, am almost certain, that the water came from the Dakota Formation (Cretaceous).  In fact, many of the smaller communities around Chamberlain use culinary water that is termed “artesian”.  I presume that the community wells are free-flowing” and capped, or perhaps pumped from a shallow depth.  I do know that on more than one occasion I became quite ill with the “SoDak Trots” after consuming “artesian” water!  In addition, Red Lake, about 10 miles east of Chamberlain near the community of Pukwana, has an adjacent free-flowing well producing warm water.  I visited the area several times during the fall and winter months to observe wild fowl visiting these ice-free waters.  Red Lake is some sort of a blow out depression rather than a prairie pothole or kettle.  It retains water during times of sufficient rain/snow and has so at least since 1993. 

But, back to Woonsocket. The headlines of the July 13, 1906, edition of the Woonsocket Times reads: The World’s Greatest Artesian Well Being Destroyed.  The story goes on to state: Woonsocket’s famous artesian well, the greatest in the world, which in its prime flowed 8000 gallons per minute and had a pressure of over 153 pounds to the square inch, must go.

     J.H. Janssen commenced work to plug the well yesterday morning.  There is a leak of about three hundred gallons a minute flowing out of the side of the well and running off to the south.  Where this water come from is a conjecture.  The well at the top consists of three pipes.  The well originally was a six inch and was drilled about eighteen years ago (1888).  It was never properly cased and the six inch casing was never put down to the rock.  This let in mud from below the piping and at times the well would flow and throw out large quantities of mud and sand.  In the early days, it was the custom to turn the well on full tilt whenever there was a crowd of people in town or when some distinguished stranger came to town.  Finally the well stopped up and after trying in vain to get it all right again the city council had it re-cased from top to bottom with a four inch casing which was placed inside the six inch casing of the old well.  As it still leaked an eight inch casing was put down about sixteen feet over both the other casings and the bottom of the new eight inch casing was attached to the outside of the six inch casing.  This makes three casings at the top of the well.  The valves were all attached to the eight inch covering of casing…

  There is quite a sentimental feeling that the well which made Woonsocket famous so far and for so long should not be destroyed but should be preserved if it is possible.  Woonsocket owes much to the well.  It has given us the best system of fire protection that exists in the state.  It has allowed us to grow more trees than there is in any other town in the state, and has saved its cost many times over.  But its period of usefulness is now over and it must go.  When it is destroyed,  Woonsocket’s most famous possession will be destroyed. 

Sometime after the destruction of the large well, the city drilled a smaller well (1920’s?), down to the Dakota (~700-800 feet), and the result is the beautiful fountain that visitors may see today---a plume spouting the air and forming Lake Prior.

As a final, somewhat off the wall note, a website promoting Woonsocket states:  An interesting fact about Woonsocket is that it missed being the Post Cereal Company headquarters by refusing to give land on which to build the factory to a stranger named Post. Post considered Woonsocket a good site – in “the heart of the grain belt” as he said. When refused, Post took his proposal to Battle Creek, Michigan, where he opened his mutli-billion dollar business.  http://www.travelinfomap.com/City_Woonsocket.html

 

mike

GONIOBASIS SPHERE

A HAND-MADE SPHERE OF GONIOBASIS IN MICROCRYSTALLINE QUARTZ FROM THE GREEN RIVER FORMATION, SOUTHWESTERN WYOMING.  THE TWO "BRIGHT" SPOTS ARE REFLECTIONS FROM THE LIGHT SOURCE.  THE WIDTH OF THE SPHERE IS ~8.75 CM.

At the recent AFMS show in Minnesota, I noticed a number of specimens labeled “Turritella Agate” that were offered for sale.  I always sort of flinch when I see that term since the specimens are not agate (in the true sense of agate being banded or included), and second, the fossils contained are not the gastropod (snail) genus Turritella ( a marine form).  But, I have come to sort of accept the term since the name “turritella agate” is well entrenched in the rock and mineral literature, and certainly specimens are sold as such in hundreds of rock shops and shows.

The “turritella agates” at the AFMS show were collected from southwestern Wyoming in the Green River Basin at a locality termed the Delaney Rim.  The Green River Basin was the site of a large freshwater lake during the Eocene Period of the Tertiary (34 my—60 my) termed Lake Gosiute, a body of water that teamed with life—including millions of high-spired snails of the genus Goniobasis or Elimia. 

It appears that the term “turritella agate” is here to stay in the rock and mineral trade.  However, savvy rock hounds will know that the snail is not Turritella and that the mineral is really not a banded agate (but is a microcrystalline quartz).  Whatever the case, a nice polished specimen is a wonderful addition to any collection.  I acquired my sphere from a close friend in Salt Lake City, Jim Madsen (now deceased).

SOUTH PARK: MAMMILLARY CHALCEDONY

A BEAUTIFUL AND QUITE LARGE (PENNY FOR SCALE) PIECE OF MAMMILLARY CHALCEDONY.

On a sunny morning last week I woke up with a thought about mowing the lawn, not an activity I really cherish.  But then some words of Walt Whitman jumped into my mind: I believe a leaf of grass is no less than the journey-work of the stars.  So, I reasoned that no person would want to destroy the work of stars and therefore a field excursion/road trip was in order!  Where to?  How about South Park?  Grabbing a large black coffee and a friend, off we went  for a day of mineral hunting with an another friend acting as a “private guide”.  There are a couple of great “things” about South Park: 1) good morning coffee, second cup for me,  and after-hunting ice cream may be found at the Bayou Salado store in Hartsel; and 2) there are some really interesting microcrystalline quartz varieties available, including petrified wood and colored chalcedony.  In addition to the coffee/ice cream, Dave and Lark at the store might give you a hint about collecting, or sell you some of their minerals or handmade jewelry.

South Park is both a topographic and structural basin, and along with North Park and Middle Park, owe their existence to the major mountain building event in the area, the Laramide Orogeny (late Cretaceous to Eocene).  Generally termed Intermontane Basins, North, Middle and South Parks are large synclinal basins complimenting the large anticlinal mountain ranges surrounding them.  

The eastern boundary of South Park is the Front Range (and its numerous subdivisions) and that demarcation is generally a large thrust fault (Elkhorn Fault).  In some localities along the eastern edge of the basin the Precambrian rocks of the mountains have been thrust about seven miles over the basin rocks (McGookey, 2003).  The western boundary of the basin is the Mosquito Range with a variety of Paleozoic rocks dipping under the basin-fill rocks.  Near the south end of the Mosquito Range are two peaks that seem quite prominent and very visible—Buffalo Peaks.  The rocks composing these peaks are volcanic in nature, including the Buffalo Peaks Andesite and various ignimbrites (hot churning gases and debris flowing by density from an eruptive center), and were deposited in a paleovalley during the Eocene-Oligocene.  Today, because of erosion, these old valleys are now high mountains and are an example of topographic inversion.  The north boundary of South Park includes several intrusive stocks of Laramide age.  The south boundary is perhaps the most interesting because of the large volcanic centers, including the Thirtynine Mile and Guffy volcanics (part of the Central Colorado Volcanic Field: CCVF).  Eruptions from these centers blocked the south outlet of the Basin and created a large lake and finally forced an eastward flowing outlet that was superimposed across the Front Range (McGookey, 2003).

PARK COUNTY, COLORADO.

At Hartsel, CO 9 and Park County 53 head south from Hartsel toward the small community of Guffy (CO 9) and the Thirtynine Mile Volcanic Area, a small remnant of the much larger CCVF.  Ash and other eruptive rocks from the CCVF cover an area of approximately 8500 sq. mi. including most of the “Sawatch Range, southern Front Range, Wet Mountains, northern Sangre de Cristo Range, and the areas between. Outflow aprons extended onto the High Plains to the east, merged with the San Juan volcanic field to the southwest, and overlapped the Colorado Mineral Belt on the north and west” (McIntosh and Chapin, 2004).  The major volcanism came from at least 10 calderas or eruptive centers with dates over a 10 million year span in the late Eocene into the Oligocene (38-29 Ma); however, volcanic activity continued into the Miocene (Wallace and others, 1999).  Post depositional faulting, dissection and erosion have produced the current landscape.

It was in this area of weathered volcanics that I was hunting for petrified wood, jasper, agate and chalcedony---and was quite successful.  Several localities produced good specimens and some of the wood was opalized in various colors.  But the most fantastic specimen I observed was a quite large piece of mammillary chalcedony, a beautiful and fantastic specimen.  The ultimate source of this specimen was most likely a vug in the volcanic rocks but weathering had left the piece exposed in a short-grass field.  But alas, it was not mine to take home; however, I do have the photos for remembrance!  

Coming back home across Wilkerson Pass a sort of peace descended upon me as I was again thinking of Whitman: Keep your face always toward the sunshine - and shadows will fall behind you.

REFERENCES CITED

McGookey. D. P., 2003, Geologic Wonders of South Park, Colorado with Road Logs: unknown binding. 

McIntosh, W. C. and C. E. Chapin, 2004, Geochronology of the Central Colorado Volcanic Field: New Mexico Bureau of Geology & Mineral Resources, Bulletin 160. 

Wallace, C. A., J. A. Cappa and A.D. Lawson, 1999, Geologic Map of the Gribbles Park Quadrangle, Park and Fremont Counties, Colorado:  Colorado Geological Survey Open-File Report 99-3 (with map).

A MODERN MINING BOOM

LOOKING WEST TO CACHE CREEK PLACER AREA AND THE SAWATCH.

 The Bureau of Land Management (BLM) has a citizen’s advisory group termed the Resource Advisory Committee (RAC).  I serve on the Front Range RAC with headquarters (BLM District Headquarters) in Canon City, Colorado.  At our recent quarterly meeting, held in Salida, the RAC had an opportunity to visit the gold placers along and near the upper Arkansas River.  The BLM has authority over much/most of the public land along the river from Leadville to Canon City and beyond to Pueblo.    They manage (very well in my opinion) the river for a variety of activities (often in conjunction with Colorado Parks and Wildlife as the Arkansas Headwaters Recreation Area) including fishing, hiking, mountain biking, camping, rafting and other water activities, and recreational gold prospecting.  Campgrounds (Railroad Bridge, Hecla Junction, Ruby Mountain, Rincon, Vallie Bridge, and Five Points) are well maintained and busy in the summer months; prospective campers should examine the possibility of making reservations.  I prefer Ruby Mountain since fishing is readily available, hiking is very nice in the adjacent Browns Canyon Wilderness Study Area (proposed as a National Monument), and pounding the rhyolite for red garnets (the “rubies”) is often productive.  Hecla Junction sits at the end of Browns Canyon and is near the site of an old fluorspar mine where “massive” (non-crystalline) fluorite may be collected.  Railroad Bridge is popular with gold panners.

MT. ELBERT, KING OF THE SAWATCH RANGE

Fishing for trout in the river is considered as world class, and a variety of river outfitters provide white water rafting, kayaking, and fishing opportunities.  However, visitors may try their skills along any of the numerous parking areas or campgrounds.

Gold panning brings many visitors to the Arkansas River and prospectors should be aware of special regulations and the fact that some claimed land exists along the river corridor.  Travelers interested in prospecting might want to examine the BLM's LR2000 database (www.blm.gov/lr2000) or contact the public room at the BLM state office for additional information (303-239-3600).  Another way to enjoy panning on the River is to join one of the local "gold clubs" such as Gold Prospectors of Colorado (www.gpoc.com) and participate in club activities.

The geology of the upper Arkansas River valley is interesting to say the least.  On the west side of the valley lays the Sawatch Range with 15 peaks, including Mt. Elbert (at 14,433 feet Colorado’s highest), exceeding 14k feet. The Valley is at an approximate elevation of ~7600 so there is a topographic relief of nearly 6800 feet.  The Sawatch Range is a large Laramide (refers to a crustal shortening mountain building event in the late Cretaceous and early Tertiary, ~72-~50 my) anticlinal structure that at one time included the southern part of the Mosquito Range east across the Arkansas River.  During the late Tertiary, a crustal extensional event culminated in a series of block faulted mountains and basins in central Colorado. The major topographic and structural feature in Colorado is the Rio Grande Rift Zone that trends from near El Paso, TX, to near Kremling, CO.  The Rio Grande River in New Mexico and Colorado, and the upper Arkansas and Blue rivers in Colorado all flow in grabens created in the fault system.  A graben is a down-dropped valley created by parallel faults on either side of the valley.  The rift system in the upper Arkansas River valley effectively split the Sawatch Anticline into two segments: the Sawatch and the Mosquito Ranges, separated by the Arkansas River.  This, and later, faulting helped create the spectacular topographic relief between the river valley and the mountains—Elbert, and other mountains, simply seem to rise straight up out of the valley.  

One particular area of interest for recreational placer miners along the upper Arkansas is an area known as Cache Creek.  Located near Granite, CO, along a creek flowing into the Arkansas with the same name, the placer area has a long history of producing gold. Discovered in 1859,  the gravels were first worked with pans and hand sluices but  low summer water flow in the creek hindered operations.  By 1863 water ditches diverting water had been dug and by 1889 hydraulic mining was dislodging tremendous amounts of gravel with major water resources being piped over the divide from Clear Creek to the south.  Most production had shut down by 1911 when Canon City and Pueblo successfully sued the gold companies for degrading (high sediment load) the water in the Arkansas River.  The BLM believes this was the first successful environmental lawsuit in Colorado.

 As with many/most former and “old” mining areas, fine gold was left behind by the hydraulic miners in the spoils area. And, for nearly 100 years the area was visited, on a somewhat sporadic basis, for recreational panning.  In 2000, the BLM acquired in excess of 2100 acres from the Conservation Fund.  The original goal of the BLM, in acquiring the acreage, was to help protect critical elk and riparian areas along the creek; recreational access was secondary in nature.

Since the Cache Creek acreage was acquired through a “recent direct purchase”, the General Mining Laws (43 CFR 3809) do not apply---the land cannot be claimed by private individuals or groups.  So, the BLM assumed that placering usage at Cache Creek would remain low (180 operating days) and therefore allowed the use of mechanical sluicing or high banking in a 26 acre core area.  The agency envisioned small scale recreational panning and sort of a “family orientated” activity.

A MINER OPERATING A HAND SLUICE.

 Wrong.  The “recession” arrived, the economy tanked, the price of gold skyrocketed, and miners were somewhat successful.  In addition, Cache Creek was well advertised in “prospecting magazines/journals” and on television and soon the place was crowded and any semblance of habitat was being destroyed, especially in the 26 acre core area.  People arrived from all parts of the U.S., many staying for the entire season (Memorial Day to the end of November).  Cache Creek was “in trouble”:  trees were being undercut and presented a danger to miners, “coyote holes” were dug and in danger of collapsing, water was being illegally diverted from private lands upslope from the BLM plot, sedimentation was vastly increasing, and miners were often in conflict with each other.  Cache Creek often resembled the boom mining areas of 150 years ago!

LARGE PITS AND COYOTE HOLES REMAIN FROM HIGH BANKING.

 The BLM needed to take steps to control the situation and begin doing so at the start of this decade: a camp host was installed to help with dispersed camping problems and try to answer questions of visitors, undercut tree were eliminated and other large trees were marked with orange rings to signify “no undercutting”, law enforcement and other BLM personnel made more frequent visits, and mechanical sluicing (high banking) was eliminated.  “Things” have improved but the BLM needs to formulate additional plans and locate resources to pay for the mitigation.  For example, usage remains high, increased sedimentation is an increasing problem, and the diversion of water on private land seems illegal (my opinion).  The RAC and the Royal Gorge Field Office will work together to formulate options.  

MINERS OFTEN TRY TO "CLAIM A SPOT".

mike     

WHAT IS THAT GREEN STUFF? "MEDMONTITE"

CHRYSOCOLLA (FORMALLY KNOWN AS MEDMONTITE) FROM THE OK MINE. WIDTH IS 3.75 CM.

I love green minerals (but also red, blue, purple, etc.)!  Perhaps the copper content in many green minerals catches my eye?  Perhaps my fondness is due to various color deficiencies in my sight---I can “see” bright green minerals but have serious problems noticing more subdued green objects—like the green stoplights mixed in with various city lights.  I try to avoid driving in a city during Christmas celebrations, or at least have a stoplight spotter in the passenger seat!  So, I am always combing the hills and deserts for bright-colored minerals.

In the early 1990’s I was working on an Environmental Impact Statement (EIS) for a new petroleum pipeline that would run from southwestern Wyoming diagonally across Utah to near St. George and then on to southern California.  This was a great project and I hoofed many a mile looking for occurrences of important fossils.  The line crossed the Mineral Mountains near the Utah town of Milford (southwestern Utah) so I was able to take a closer look at several of the old mining areas to the west of town. 

The Beaver Lake Mountains are situated to the northwest of Milford and contain several small copper prospects and mines.  Some are skarn-type copper deposits (altered Paleozoic limestone) while others (i.e. the OK Mine) are copper porphyry deposits hosted in quartz monzonite; many produced a few thousand tons of copper in the early-to-mid 1900’s (Wilson, 1995).  In rummaging through mine dumps along the road near the OK Mine I picked up a small piece of greenish-colored something or other, called it malachite, and threw it in my bag.  We ran into a local mining geologist who said that I had a piece of medmontite, a name with which I was completely unfamiliar (and essentially am today)!

In getting ready for my CSMS presentation in September (the 20^th; Rockin’ Thru Utah), I was trying to gather together my Utah specimens and came across this long forgotten piece of medmontite.  So, the first thing that I did was to search the internet, and my books on Utah---not much luck.

   Mineral Data (www.mindat.org) noted medmontite was named in 1950 (Chukhrev and Anosov) and described as “a copper bearing mineral of the montmorillonite group”---it seemed to be a copper infused clay (and a synonym of cupromontmorillonite).  The presence of copper would explain the green color.  But, MinDat further noted that medmontite was discredited as a distinct species and was “simply” a mixture of chrysocolla and montmorillonite.  

So, my question was: what do you call the specimen?  And, I still don’t know the answer but I guess chrysocolla.  MinDat is mum on the subject and virtually no internet resources describing the discredited mineral could be located.  The closest I came was to note a crystal store in Oxfordshire, UK, selling medmontite specimens (£4.99 plus shipping but including VAT) from the OK Mine that are  “dead ringers” for my small piece.  They describe medmontite as a mixture of chrysocolla and mica that “is a stone of harmony”!

Wilson (1995) listed the following minerals from the OK Mine: malachite, azurite, bornite, chalcopyrite, pyrite, cuprite, brochantite, molybdenite, and chrysocolla.  Therefore, I guess I will go with chrysocolla, a hydrated copper silicate-- (Cu,Al)₂H₂Si₂O₅(OH)₄·nH₂O (but it still looks like malachite to my untrained mineralogical eye)!

mike 

PHOTOMICROGRAPH OF ABOVE SPECIMEN (2.40 MM WIDTH).

REFERENCES CITED

Chukhrev, F.V. and F. Y. Anosov, 1950, Medmontite, a Copper bearing Mineral of the Montmorillonite Group: Vses. Mineralog. Obshch. Zapiski, ser. 2, 79(1), 23-27.

Wilson, J. R., 1995, A Collector’s Guide to Rock, Mineral & Fossil Localities of Utah: Utah Geological Survey Misc. Pub. 95-4, 148 p.