Small Format Aerial Photography:

Cripple Creek Mining District, Colorado

By Steven Wade Veatch

Introduction

   Known as "America’s greatest gold camp," Cripple Creek grew from just a few people in 1890, when gold was first discovered by a cowboy named Bob Womack, to a population of 60,000 during its heyday. The six square mile gold mining district, located on the western side of Pikes Peak, was established in 1891. Womack’s initial discovery was a small placer deposit yielding less than 500 ounces of gold.

Overview of Cripple Creek Mining District. View to the west. City of Victor is to the left of the large open pit mine. Photo date 3/99 by S. Veatch.

   Soon high-grade gold veins were being followed underground by hordes of miners with picks and shovels. By 1900, the district had over 500 active mines and during the district’s 107-year history it produced more than 21 million ounces – making it the third largest gold mining district in the United States. Production peaked before World War I, then declined.

   The city of Cripple Creek has undergone many rapid changes recently when mining was resumed and limited-stakes gambling was legalized. The majority of the mining property in the district is controlled today by the Cripple Creek and Victor Gold Mining Company, a joint venture between Pikes Peak Mining Company and Golden Cycle Gold Corporation. Seven large deposits have been identified: one is in production (Cresson), two have been mined out (Globe Hill and Iron Clad), and four are being explored. Recent exploration has defined a proven reserve of over 2.6 million ounces with an additional resource of 1.4 million ounces (Pontius, 1996). The Cripple Creek and Victor Gold Mining Company has produced over 350,000 ounces of gold since 1989.

   About 32 million years ago a volcanic complex was emplaced near Cripple Creek. The emplacement is thought to be associated with the start of the Rio Grande Rift. The Cripple Creek volcanic complex has several explosive vents localized along a central fissure (diatreme), composed of a breccia (fragments of angular rock), intruded by a series of phonolite dikes and sills which display shattered textures. The intrusive and extrusive activity within the Cripple Creek volcanic complex may have lasted between three and four million years.

   Mineralization closely followed the emplacement of the volcanic complex, with most of the gold localized along structural zones within the volcanic complex. About 30 million years ago mineral rich fluids moved up from great depths and seeped into cracks and fissures where they cooled into hard ore-bearing veins. The process of mineralization continued for about two million years. The ore body occurs as low-grade disseminated, microcrystalline native gold attached to pyrite and as deposits of narrow high-grade gold telluride veins with quartz, pyrite, rutile, and fluorite. Most of the gold mined in the early days of the district came from the high-grade gold telluride veins.

   Gold in the mining district occurs in the Tertiary alkaline rocks of the volcanic complex. The surrounding country rocks are Precambrian granite and metamorphic rocks that comprise four rock units: biotite gneiss, granodiorite, Cripple Creek Monzonite, and Pikes Peak Granite (Wobus et. al. 1976).

Cresson Project open pit mine. This photo depicts the mining cycle of "drill, blast, muck, and haul." The bench is blasted with amonium nitrate shortly after the three drill rigs have drilled a pattern. Note grid where blasting has occurred. Mucking (shoveling) is done with CAT loaders. Hauling is accomplished at the mine with 85-ton haul trucks that remove the low-grade ore to be crushed. Over 24,000 tons a day go through the gyratory crusher. The crusher reduces the ore to fragments about 1.5 inches. This material is placed on a heap leach pad for the extraction of gold. All heavy equipment drives on the left side of the road so the driver can always see the edge of the road for safety reasons. Toward the bottom of the photograph is the collapsed collar of a 19th century vertical mining shaft. It appears as a circular depression. At the surface extra timbering was built around the collar to keep surface material from caving in. Since the collar is so close to the surface the timbers rot away, allowing the surrounding area to subside. Photo date 3/99 by S. Veatch.

 

Cresson heap-leach pad. Crushed ore is hauled to this site where it is treated with cyanide. The cyanide solution percolates through the ore and dissolves the gold. The solution is pumped to an adsorption plant where it flows through carbon adsorption tanks. The activated carbon physiochemically adsorbs the gold into the carbon, resulting a 95 % recovery rate of gold from the solution. Photo date 3/99 by S. Veatch.

      

High oblique southeast view of the Cresson Project open pit mine, the site of the historic underground Cresson mine. The old Cresson mine was the second largest producer in the district. Laser devices are used to maintain benches at 25 feet. Ground penetrating radar (GPR) is used to detect historic underground workings. This prevents heavy equipment and miners from falling into deep underground stopes (mined out areas). Photo date 3/99 by S. Veatch.

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Cripple Creek Ore Minerals

       

Sylvanite is one of the gold-silver telluride minerals that occurs in the district. This mineral was first found in Transylvania. From the Richard Titmas collection. Photo date 4/99 by M. Estlick.

         

Calaverite and fluorite on phonolite. From the Richard Titmas collection. Photo date 4/99 by M. Estlick.

        

Marcasite forming cockscomb crystal groups. Marcasite is identical to pyrite in composition except for a slightly higher sulfur content. From the Richard Titmas collection. Photo date 4/99 by M. Estlick.

Photo Acquisition

   Small format aerial photography (SFAP) provides low-height, large-scale imagery using lightweight cameras with a 35-mm or 70-mm format. Lifting platforms are varied and can include small aircraft, gliders, kites, blimps, and balloons. SFAP has the advantage of aquiring imagery that could not be obtained by larger aircraft and at significantly lower cost. SFAP is used primarily in mapping and to evaluate natural and cultural resources.

 

  The photographs for this project were acquired on March 27, 1999 between 10:00 a.m. and 10:30 a.m. The morning was partly cloudy with a slight breeze.   

  The airplane used for the project was a Cessna 172 M. This small aircraft was flown over the target high enough (on average 500 feet above the ground) to capture the target in a single frame.

   A Pentax 160 35mm camera was used. Due to air currents that rock the plane, both 200 and 400 film speeds worked well to reduce blurring. A simple HP flatbed scanner was utilized to scan color photographs with 24-bit color at a resolution of 600 dpi adequate for low-elevation aerial photographs. The conversion of the photographs to a digital format (JPEG-Joint Photographic Experts Group) allows the application of computer processing, handling, storage, analysis, and image enhancement. Image processing was performed with Paint Shop Pro V 5.0.

Acknowledgments

   This report is part of an earth science course requirement (ES 555 Small Format Aerial Photography) completed at Emporia State University. Much of the information presented in this report was gained from a number of recent field trips undertaken by the author at the mine and from on-site mining company personnel Ed Hunter, mine engineer and David Vardiman, chief exploration geologist.

References

Pontius, J.A., 1996, Field guide to the gold deposits of the Cripple Creek mining district, Colorado, USA: Geological Society of America Annual Meeting, Guidebook for Society of Economic Geologists Field Trip No. 1, Nov., 1996, 9 p.

Wobus, R. A., Epis, R. C., and Scott, G. R., 1976, Reconnaissance geologic map of Cripple Creek-Pikes Peak area, Teller, Fremont and El Paso counties, Colorado: U.S. Geological Survey Map MF-805.

April 15, 1999