FIELD REPORT
EL CAPITAN IRON DEPOSITS,
LINCOLN COUNTY,
NEW MEXICO
March 20, 2007
Kwaku Boakye
Leann M. Giese
Industrial Minerals Class
With Virginia Mclemore and Jim Barker
NEW MEXICO TECH
801 Leroy Place, Socorro, NM 87801
Abstract
Students from New Mexico Tech spring 2007 Industrial Minerals Class visited the old
Smokey Mine in south central New Mexico on March 12, 2007 to learn the history,
geology and mineralization of the mine area. The Smokey Mine sits in the Capitan iron
deposits of Lincoln County in southeastern New Mexico. The main El Capitan deposit
falls along State Highway 48/NM-246 driving north from the town of Capitan.
The iron ore is predominately magnetite. Other associated minerals are hematite,
goethite, and limonite. The principle gangue mineral is calcite with smaller amounts of
quartz, epidote, garnet, and tremolite present. The iron mine is a shallow open pit
approximately 1300 feet in diameter. The actual deposit, determined by drilling, is about
2000 by 3000 feet in area, and 100 to 400 feet thick.
The ore was exploited using the open pit mining method, and materials were transported
by truck and conveyor belts. Processing involved crushing and screening to liberate the
iron ore. Mining ended in 2000 due to low demand and currently there is no mining. El
Capitan Precious Metals, Inc. has recently explored the property for the potential of other
metals in the deposit. Laboratory results indicate both gold and platinum at economical
ore grade values.
This was a great opportunity for the students to see an iron deposit in-place, as well as
some other minerals that are associated with iron deposits. Samples were collected for
our rock kits designed to show the various industrial minerals mined in New Mexico.
This kit will be given to New Mexico teachers enrolled in New Mexico Techs’ Master of
Science Teaching program as an aid to help them teach students about the industrial
minerals of New Mexico.
Introduction
The Capitan mining district has been known since the turn of the century. The Capitan
iron deposit was explored and quickly recognized as one of the largest occurrences
(Kelly, 1996). The iron deposit is predominately magnetite replacing limestone, a
common constituent of central New Mexico formations. The discovery of the iron deposit
was instigated by the aggressive Spanish intension to find gold in the area after the recent
discovery in the Jicarilla district and at White Oaks.
After discovery, a tremendous amount of exploration was initiated and development of
mines started during World War I. By 1921, approximately 35,000 tons of iron ore were
produced (Smith, 2007). There was a decline in production after the war. Interest in the
Lincoln County iron ores was revived during World War II, but production was limited
due to the small size of the individual ore bodies and increased the shipping charges
during that time. These conditions resulted in mining disruptions and possible closure of
the mines. During 1942 and 1943, a little over 16,000 tons were produced and shipped
but wartime conditions made mining unprofitable. Mining production totaled 59,725 tons
up to 1957. The production at the Smokey Mine around 1991 was roughly 10,000 to
15,000 tons depending on demand (Barker, 1991). The area of this iron mine continues to
be recorded as one of the most immense iron deposits in New Mexico of the 20th century.
The long history and the economic impact of the Smokey Mine have mounted a large
amount of research and study in the area. New findings from exploration have indicated
the possibility of mining gold and platinum from the deposit. Based on this, a graduate
Industrial Mineral Class filed trip was organized by Dr. Virginia T. McLemore to visit
the mine on March 12, 2007. This report meets assignment requirement of the class and
also shows the level of assimilation of information by the students who attended the field
trip and also reviews in the literature on the Capitan iron deposits.
Location and Property description
The old Smokey Mine sits in the Capitan iron deposits of Lincoln County, New Mexico
(Figure 1). These deposits lie to the East of the Capitan Mountains almost directly
between the towns of Carrizozo and Roswell. The Bureau of Land Management has 331
lode claims in the area and the other four are patented claims.
The total claim block occupies approximately ten square miles. The main El Capitan
deposit falls along the State Highway 48/NM-246, 5.7 miles north from the town of
Capitan, New Mexico. The mine is accessible by dirt roads. Currently, there is a
company shop along with other storage and equipment buildings and miscellaneous
conveyor belts and crushers on the property.
Figure 1. Shows a detailed map projected from a New Mexico map indicating the
location of the Capitan Mountains where the iron deposit is located (McLemore,
1996).
Geological Description and Mineralization
The Capitan deposit extends from the east side of the Capitan Mountains to just east of
Bingham, and to the north edge of the Gallinas Mountains. This is the intersection of the
north-south-trending Pedernal uplift and the east-west-trending Capitan lineament. The
Capitan iron deposit rests in the Capitan Valley, a west-plunging syncline. To the west,
the rocks become younger as one travels from Hondo and Lincoln westward towards
Carrizozo (McLemore, 1996). Figure 2 shows a simplified geologic map of the Capitan
area. Within the area of Capitan (indicated with cross hatching) is the Morrison
Formation (host rock for the iron deposits) of Jurassic age found in the roadcut of NM380 east (Lucas, 1991).
Figure 2-Simplified geologic map of the Capitan area (simplified from Kelly, 1971;
Bodine, 1956)
To the northwest of the Smokey Mine property there is a 300 meter thickness of San
Andres sandstone exposed and overlain by sandstone of the Triassic Santa Rosa
Formation. The San Andres Formation is faulted against sandstone of the Upper
Cretaceous Dakota Group between the Smokey Mine and the town of Capitan to the
south.
The host rocks associated with the iron deposit is Permian San Andres Formation
limestones, shales, and sandstones. There are brecciated areas and slickensides exposed
around the pit as well, indications of faulting in the area. The Capitan aplitic intrusives
are 60 to 120 meters below the surface as indicated by drilling. These small silica-poor
intrusions are plug-like or laccoliths. The iron deposits are small pod- or lenticular-like.
Kelly (1952) thought the mineralization was from the fluids associated with the Capitan
intrusive cooling and crystallizing. Kelly also interpreted the deposit as a mineralized
sinkhole that formed before the Capitan aplite intrusion. Recent mining has not yet
disproved this theory, and there are many other sinkholes in the San Andres Formation to
the north of Capitan Mountain (Smith, 2007).
The iron ore at the mine is primarily magnetite that has some hematite, goethite, and
limonite. The magnetite occurs massively and as disseminated, fracture fillings and
limestone replacement. There is calcite (the principle gangue mineral) and smaller
amounts of quartz, epidote, garnet, and tremolite present. The present of slickensides in
the deposit is shown in Figure 3.
Figure 3. Close up view of slickensided minerals in the iron deposit area (photo:
Leann M. Giese)
Mining and Processing
Exploration Work
The quest to explore and find more iron deposits initiated the first drilling project near
Capitan in 1944. A sampling program was soon drafted and implemented. Drilling was
accomplished with wagon drills and 9-m steel rod. The original drilling program was
challenged by the difficulty of drilling through the vuggy zones in the ore. Exploration
between 1947 and 1948 showed a substantial reserve of 1,000,000 tons of 45% iron ore
(Kelly, 1949). Figure 4 is the deposit area where exploration was done
Figure 4. Dumps in the area of the Smokey Mine iron deposit (photo: Leann M.
Giese)
The abrupt fall of iron prices and problems indicated earlier made the mining of the iron
no longer of interest. But old mine records indicated the possibility of gold and platinum
exist within the deposit. This initiated another exploration program to determine the
possibility of finding economic reserves of gold and platinum. El Capitan Precious
Metals, Inc. has recently explored the property for the potential of other metals in the
deposit. Laboratory results indicate both gold and platinum at ore grade values of 0.020
opt (ounces per ton) and 0.011 opt respectively. Table 1 is a summary of metallurgical
assay results reported by Smith 2007. Reports indicate a possible strip ratio of 8 to 1.
The actual deposit, determined by drilling, is about 2,000 by 3,000 feet squared and 100
to 400 feet thick.
Table 1. Metallurgical lab assay results from extraction, ounce per ton (Smith,
2007).
Sample
EC-1
EC-10
EC-11
EC-16
EC-22
EC-24
Au
Calculated
Head
Grade
Sodium
Cyanide
0.017
0.086
0.089
0.015
0.018
0.029
0.011
0.079
0.081
0.009
0.011
0.023
Au recovered
Sodium
Sodium
Cyanide
Thiosulfate
Chlorine
0.014
0.080
0.084
0.011
0.014
0.025
0.012
0.081
0.082
0.010
0.011
0.022
Average %
Recovered
72.6
98.3
92.5
66.7
66.7
80.5
Pt
Calculated
Head Grade
0.023
0.050
0.023
0.044
0.015
0.019
Sodium
Cyanide
Chlorine
0.019
0.046
0.016
0.030
0.009
0.016
Pt recovered
Sodium
Average %
Thiosulfate Recovered
0.011
0.032
0.011
0.030
0.010
0.011
Production
Mining of the iron ore deposit used an open pit technique. Open pit mining was used
because it was a surface deposit that did not extend very deep below the surface and was
of low grade. Open pit mining uses a load and haul technique. The iron mine is a shallow
open pit approximately 1300 feet in diameter. In general, pit designs are planned to
achieve maximum profits, as was this one. Ore and waste were hauled to waste dumps or
Run of Mine (ROM) dumps using trucks and conveyor belts. Past production is estimated
to have been approximately 200,000 to 250,000 tons of ore produced from the Smokey
Mine pit in 1975 when the deposit was taken over by H.D. Larue and sons. Around 1991
the production was around 10,000 to 15,000 tons depending upon the local demand.
The last production of ore from the mine was in 2000 (Smith, 2007). Figure 5 shows the
some of the old pits in the mine area.
Figure 5. Dr. Virginia McLemore and students standing on filled old Smokey Mine
pit sites (photo: Leann M. Giese)
65.2
78.0
58.7
68.2
63.4
71.1
Processing
Iron ore mined is processed by running the ore through a coarse crushing circuit, then
through a screening process (10-20 mesh) where the passing material moves over a
magnetic head pulley that separates the magnetite from the rest of the rock. The ore is
shipped and the tailings used locally for road and driveway aggregate. Figure 6 shows a
picture of the type magnetite from which iron is commonly processed.
Figure 6. Magnetite ore from which iron is obtained by crushing and screening
(http://www.mii.org/Minerals/photoiron.html)
Uses
Metallic iron in its pure state is reactive and corrodes quickly, especially in moist air or at
elevated temperatures. The iron metal has transition points at 700, 928, and 1530°C.
Iron is hard, brittle, fairly fusible, and is often used to produce other stronger alloys,
including steel. Wrought iron contains only a few tenths of a percent of carbon, is tough,
malleable, less fusible, and usually has a "fibrous" structure.
Carbon steel is an alloy of iron with small amounts of Mn, S, P, and Si. Alloy steels are
carbon steels with other additives such as, nickel, vanadium, etc. Iron is a cheap,
abundant, useful, and important metal. Its wide range of chemical and physical properties
make gives it diverse uses in industry, construction, and agriculture.
Magnetite, mined as iron ore, has a versatile usage. It serves as a natural magnet.
Magnetite is also used as a dense aggregate for civil engineering, building foundations,
ground stabilizers, and vibration dampening. In water treatment, magnetite is use to
remove impurities, algae, color and turbidity. It is also used as counterweights in
excavators, ship loaders/unloaders, and even in washing machines because of its high
density. Magnetite plays an important role in heat storage. In manufacturing cements,
magnetite is an indispensable component added to give it’s a high-strength.
Conclusion
The deposit at Smokey mine continues to be one of the largest iron deposits discovered in
New Mexico during the 20th century. El Capitan Precious Metals, Inc. has recently
expressed interest in the deposit for its recoverable gold and platinum potential.
Extensive drilling and mapping has been carried out for the past few years but further
analysis needs to be done.
This was a great opportunity for the students to see an iron deposit in-place, as well as
some other minerals that are associated with the deposit. Samples were collected for rock
kits design to show the various industrial minerals occurring in New Mexico. This kit
will be given to teachers as an aid to help teach their students about the industrial
minerals of New Mexico.
References
Barker, J. M., Kues, B. S., Austin, G. S., and Lucas, S. G., 1991, Notes on the Smokey
Mine, Capitan Iron Deposits, Lincoln County, New Mexico. In: Geology of the Sierra
Blanca, Sacramento and Capitan Ranges, New Mexico, p. 42-44.
Bodine, M. W., Jr., 1956, Geology of the Capitan coal field, Lincoln County, New
Mexico: New Mexico Bureau of Mines and Mineral Resources, Circular 35, 27 pp.
Kelley, V. C., 1949, Geology and Economics of New Mexico iron-ore deposits:
University of New Mexico, Publications in Geology, v. 2, 246 p.
Kelley, V. C., 1952, Origin and pyrometasomatic zoning of the Capitan iron deposit,
Lincoln County, New Mexico: Economic Geology, v. 47, p. 64-83.
Kelley, V. C., 1971, Geology of the Pecos country, southeastern New Mexico: New
Mexico Bureau of Mines and Mineral Resources, Memoir 24, 78 pp.
Lucas, S. G., 1991, Southeasternmost outcrops of the Morrison Formation, Capitan,
Lincoln County, New Mexico; in Barker, J. M., Kues, B. S, Austin, G. S., and Lucas, S.
G. (eds.), Geology of the Sierra Blanca, Sacramento, and Capitan Ranges, New Mexico:
New Mexico Geological Society, Socorro, Guidebook 42, p. 41.
McLemore, V.T., 1996, Smokey Bear State Park: New Mexico Geology, v. 18, p. 104107. http://geoinfo.nmt.edu/tour/state/smokey_bear/home.html (accessed March 19,
2007)
Smith, C. L., 2007, Report on El Capitan Gold-Platinum Project, Including Indicated
Resource Calculations, Lincoln County, New Mexico. El Capitan Precious Metals, Inc.
P.1-23. http://www.elcapitanpmi.com/ (accessed March 16, 2007)
http://www.corrosionsource.com/handbook/periodic/26.htm, (accessed March 19, 2007)
http://www.mii.org/Minerals/photoiron.html, (accessed March 19, 2007)
http://www.phelpsdodge.com/AboutUs/OurCompanies/Mining/MiningProducts/Magnetit
e.htm