Centralia Mine Fire Analysis:
Presence of Sulfur-bearing Mineral
Deposits at Thermal Vents

Matt Livingood
Jason Winicaties
Jared Stein


ESL 201 – Fundamental Techniques in Geology
Dr. C. Gil Wiswall
December 15, 1999


Centralia Coal Fire Analysis: Presence of Sulfur-bearing Mineral Deposits


Since 1962, a coalmine fire has spread underneath the surface of Centralia, located in the anthracite coal region in Columbia County, Pa. In Centralia, many measures have been taken to cope with the various problems resulting from the fire. Ultimately, almost the whole town has had to relocate to other areas due to fear of subsidence, water contamination, and air pollution from the noxious gases released through vents and fumeroles. Solid, multicolored deposits can be found on the surface surrounding these vents. The deposits are believed to be primarily sulfur-bearing minerals deposited hydrothermally on the surface by the escaping vapors. In this experiment, we collect five different deposits located around three different vents and one deposit located on an anthracite sample nearby a vent. We evaluate the six samples for mineral content, via X-ray diffraction analysis. The results indicate that all conclusive (3) vent deposits are sulfur-bearing minerals and one particular sample, on the anthracite, is native sulfur. The native sulfur, found on an anthracite sample rather then the surface surrounding a vent, is deposited from bacteria called Desulfovibrio desulfuricans. The bacteria use the carbon in the coal for energy and reduce anhydrite (CaSO4) and gypsum (CaSO4·H2O) to hydrogen sulfide (H2S) (Cooney and others, 1999). The hydrogen sulfide is then oxidized upon contact with the atmosphere, leaving native sulfur (S0) behind. Other minerals found include Tschermigite and Apjohnite. Apjohnite was recovered as a coating on a rock removed from the inside of a vent. Apjohnite usually is white to pale yellow, has a hardness of 1.5 to 2, and has encrustation (forms crust-like aggregate on matrices) habit (Barthelmy, 1999). Tschermigite, also known as ammonia alum, is soft (hardness = 1.5-2.0) and is usually white to colorless (Barthelmy, 1999). Tschermigite is very rare and only found natively in Czechoslovakia, but also has been reported to form as deposits around volcanic vents and fumaroles (Lowenstern, 1999). For the tschermigite and apjohnite, the sulfur compounds release from the coal and dissolve into the heated fluid, where they react with other dissolved ions present in solution. They are then carried to and deposited on the surface by these hydrothermal fluids. At the surface, the liquids cool and the sulfur minerals are precipitated from the solution. The presence of Tschermigite suggests that the coal mine fires of Centralia are quite similar to other high temperature regions on earth, particularly volcanically active areas.


Throughout much of Centralia there are cracks and holes in the ground with a harsh steam constantly pouring out. The trees are all dead and white in color and the ground is so hot your feet sweat. There is a sulfur smell to the steam and two hours of exposure was enough to give my colleagues and I headaches. Around these surface holes, or vents, different colored deposits are scattered in a wide range of sizes. These deposits are very interesting for they exhibit various colors and forms. It is the goal of our research to collect these deposits for observation and X-ray diffraction analysis. We infer that these samples are sulfuric in nature from the smell of the vapor rising from the vents. From the analysis, we hope to conclude that these deposits are primarily sulfur and/or sulfur-bearing minerals. Also, we hope to gather enough evidence to formulate a theory on how the deposits were extracted, transported, and deposited.

We chose to research the Centralia mine fire because of the great tragedy it presents. The residents of Centralia have had their lives shattered by the fires from stress of relocation and/or medical complications. Also, we chose Centralia because the area resembles a post-nuclear war wasteland and is very unique. The sulfury smell, rocky smoking hillsides, absence of people, and ghostly white smoldering trees present an eerie landscape sparking the interest of my colleagues and I. Specifically, we chose to concentrate our experiment on the vent deposits. The deposits are unlike any other surface rocks or features we observed in Centralia and we were very curious of there nature. From the experiment, we hoped to gain an understanding of the origin, methods of transportation and deposition, and classification of these deposits. We also wish to further our knowledge of the landscape characteristics and history of the Centralia mine fire.

Centralia Fire History

Centralia is located in the anthracite coal region of Eastern Pennsylvania, in Columbia County. In the summer of 1962, a fire started in the Buck Mountain coal bed. At this time, there were about 1,100 residents with 545 families and businesses in Centralia (PDEP, 1996). The mine fire is believed to have started from an accidental fire at the landfill located at the southern end of the town. >From here, the fire spread igniting an open coalmine shaft and spreading throughout the abandoned mines. By 1983, the fire consumed approximately 195 acres of area (Logue and others, 1991), and the main road into town, Route 61, suffered severe subsidence damage (PDEP, 1996). In 1983, the Office of Surface Mining (OSM) was authorized by the Department of Health to reclaim public lands and private establishments deemed hazardous, and over 30 houses were moved away. The OSM released a report in 1983 estimating that the fire could spread to 3,700 acres and "burn for a century or more if left uncontrolled" (Logue and others, 1991). Hazards included subsidence, noxious gases, oxygen depletion, and particulate matter. "A study estimated it would cost $663 million to extinguish what some call "the granddaddy" of all mine fires", says Lynne Glover in the Tribune review. Because the estimated cost of relocation was only about 42 million, relocation was chosen as the answer to the fire. The coal bed will eventually burn out when the coal seem ends, so the neighboring towns are believed to be safe (Glover, 1998). In 1984, Congress set aside $42 million dollars and begins to relocate families and businesses. The Milton S. Hershey Medical Center released a report that concluded Centralians had higher incidences of respiratory disease, hypertension, gastrointestinal disease, arthritis, and depression in Feb. 1986 (Logue and others, 1991). In 1993, Route 61 is closed indefinitely after several attempts to repair it. The 53 remaining households are condemned but the remaining residents still refuse to leave. By 1996, there were <46 remaining residents (< 5% of the original) of Centralia (20 families) and the total costs of relocation exceed $35 million (PDEP, 1996).

Anthracite Characteristics and Geology

The anthracite coal beds of eastern Pennsylvania cover an area of about 1250 sq. km and constitute over 97% of the total U.S. anthracite resources (Funk and Wagnall’s, 1999). There is approximately 15 billion tons of recoverable coal in this region, enough to supply anthracite for the next 400 years (Centralia Coal, 1999). The anthracite coal beds were deposited in the Pennsylvanian, ~300 ma. During this period of the Carboniferous, the region was predominantly lowlands and forested swamps periodically covered by shallow seas. Trees and ferns constitute the majority of the Pennsylvanian plant life. For coal to form, the plant matter must be deposited underwater to avoid oxidation to water and carbon dioxide. The plant matter was then transformed by biochemical and physical processes (metamorphic events from subsequent orogenies) into a dense consolidated carbon-rich rock (Levin, 1996). Different coals are produced in a succession depending on time and metamorphic stress starting with peat, to lignite, bituminous, and finally anthracite (Bell and Wright, 1985). Anthracite coal has the highest fixed carbon, 93-98%, and lowest volatile material of all coals. Anthracite is a hard, glossy black rock with concoidal fracture. Although harder to ignite, anthracite (ignition at about 225° C) releases large amounts of energy (7000 - 8000 cal./ kg) when burned with less smoke and soot as bituminous (ignition at about 150° C) and lignite coals (Funk and Wagnall’s, 1999; Glover, 1998; Mottana and others, 1978).

Other Underground Coal Fires

There are other places in Pennsylvania and around the world where underground coal fires burn. Pennsylvania has over 250,000 acres of abandoned mine lands and has >1/3 of the nations mine problems. There are over 45 mine fires burning across Pennsylvania. There are five underground fires in Allegheny County, five in Percy County, one in Westmoreland, and others in more isolated areas. There are also fires in Findlay Twp., West Elizabeth, Plum, and Clinton. "In all, the DEP estimates about 1,300 acres across the state are on fire underground" (Glover, 1998). One particular town, Youngstown, is under the wrath of the Percy fire that has been burning for over 30 years. There are about 60 homes resting on top of this fire now. Youngstown is reaching the critical decision point that Centralia reached in 1983, either extinguish the fire or relocate the whole town. Estimates conclude that extinguishing the Percy fire will cost $30 to $40 million, and over $650 million to put out all nationwide fires (Glover, 1998).

A very large underground fire burns through large coal beds in Northern China. The fires consume up to 200 million tons of coal each year. This fire is quite a bit larger then the largest Pennsylvania fire (Centralia), releasing almost "as much carbon dioxide into the atmosphere as do all the cars in the United States" (Kittl, 1999). The Chinese haven’t really paid much attention to the fire until recently. Now they monitor the fire with heat sensitive satellite photographs. Areas of subsidence have caused very large cracks in the surface and there are areas where one can observe the burning beds above them on the side of a cliff. The Chinese are now taking measures such as burying the coal with dirt and pouring a water-clay mix into surface cracks to cool the fire. They feel the only way to deal with these fires is to try to isolate them and let them burn out (Kittl, 1999).

Mineralization of Sulfur

Sulfur (S) is distributed in the crust in mineral forms such as iron pyrites, sphalerite, galena, gypsum, barite, and others. It also "occurs native in the vicinity of volcanoes and hot springs" (Hammond, 1975). Sulfur is yellow, has a low specific gravity (2.0), and is brittle (Cepeda, 1994). The sulfur in the deposits comes from mineral and organic sulfur in the anthracite. The sulfur in Anthracite can be divided into three categories: pyritic sulfur, sulfate sulfur, and organic sulfur (Alvarez and others, 1997). Pyritic sulfurs, also called sulfide sulfurs, constitute anywhere between 25-75% of the total sulfur and are contained in minerals such as pyrite and marcasite (FeS2) and sphalerite (ZnS) (Chinchon and others, 1991). During combustion, sulfide sulfurs release in the form of their oxides at about 500° C.

2 FeS2 + 5 O2 ® 4SO2 + 2FeO

The organic sulfurs, 20-70% total sulfur, are sulfurs incorporated into the organic molecules of the plant material and also release around 500° C. Sulfate sulfurs usually are in the form of gypsum (CaSO4) and decompose to CaO and CO2 at 500° C. The sulfates don’t release as sulfur dioxide until 1060° C, a temperature where 13.70% of the initial sulfur still remains. Thus a large percent of the sulfur still remains in the form of anhydrites (Alvarez and others, 1997; Chinchon and others, 1991).

Sulfur oxides, primarily sulfur dioxide (SO2), are released in gaseous form into the atmosphere. For underground fires, the sulfur byproducts are, in part, dissolved into the heated surface groundwater and transported to the surface. Other byproducts are released in gaseous form. Sulfur has a low melting point (175° F) and is easily dissolved. The sulfur oxides react with other ions in the fluids and/or the atmosphere and precipitate out sulfur-bearing minerals during condensation at the cooler surface.

Native Sulfur can form if the proper conditions are met, low temperatures and the presence of an energy source. At these conditions, bacteria called Desulfovibrio desulfuricans use the carbon in the coal as the energy source (Cooney and others, 1999) in a reaction that reduces the sulfur from anhydrites (CaSO4) and gypsum (CaSO4·H2O) minerals in the coal. The sulfur is then released in the form of hydrogen sulfide (H2S), which is then oxidized in the atmosphere to form native sulfur (Cepeda, 1994).

Data and Observations

Deposit samples were collected from 3 different sites. Site 1 and site 2 are separated by approximately 100 feet and are located in a ravine on the west side of Route 61 at the subsidence damage site. Site 3 is located to the Northwest of sites 1 & 2 at the landfill where the coal beds initially caught fire.

Site 1: Site 1 was a small area at the bottom of the ravine. From Site 1, we collected one sample labeled "white crystal". White crystal deposits were scattered lightly over about a 25 sq. ft area. The "white crystal" was concentrated in roughly a 6 x 3 inch area that was located next to a fissure to the downhill. The fissure was an 8 to 10 inch crack in the surface with water seeping out and moist soil surrounding it.

Site 2: Site 2 was the surroundings of a larger fissure on the eastern side of the ravine. It was located about halfway up the hillside and steam/smoke was escaping from the hole and surrounding cracks. From this site, we collected four samples labeled: "yellow chunk", "white chunk", red chunk", and "green crystal". The red, yellow, and white chunk deposits were massive in nature, brittle, and homogenously deposited around the vent. The three different colors exhibited no visual zoning and apperared to be similar. Large masses, up to ~4 inches in diameter, displayed color changes within crystal itself. Some samples displayed all three colors within themselves.

The "green crystal" deposits were found on a relatively rectangular sample of anthracite roughly 24in. x 10in. x 3in. in size located downhill from the vent. The anthracite was charring on the underside and the crystal deposits were located on the side of the rock at the junction of the side and top faces. The anthracite sample was located about 5 feet downhill from any visual vent activity and did not appear to be associated with the vent itself at this particular time.

Site 3: Site 3 was located a couple hundred feet northwest of the first two sites, at the landfill. This area was the landfill where the fire initially ignited the coal seam. There are many fissures scattered around the area and the ground is exceptionally warm here. Site 3 is a large hole in the bedrock with steam pumping out and a white film covering all the associated rocks. The deposit is scraped from a rock taken from inside the vent. The sample appears to be a white, porous film baked onto the rock.

The samples were collected in plastic zip-lock bags and labeled accordingly. The samples were then crushed into a fine powder using a mortar and pestle. The powder was analyzed by X-ray diffraction and peaks were correlated on a sulfate database to search for sulfur-bearing minerals. Results are printed and placed in a data table.

The data table is provided in figure 1:

Figure 1

Site #

Sample name



Major mineral or component

Chemical Composition







white crystal

bright white

fine, powdery crystals










red chunk












white chunk












yellow chunk

pale yellow











green crystal


fine crystals

Native Sulfur









white porous


white, bubbly film


 MnAl2(SO4)4 × 22H2O


Results and Conclusions

The "green crystal deposits found on the anthracite sample are native sulfur. The conditions were suitable for Desulfovibrio desulfuricans to flourish. Desulfovibrio desulfuricans use carbon for energy so the carbon-rich anthracite offers a substantial source of energy. Also, the anthracite sample was on the surface so the temperatures were low enough for Desulfovibrio desulfuricans to grow. The bacteria use the carbon in the coal for energy and reduce anhydrite (CaSO4) and gypsum (CaSO4·H2O) to hydrogen sulfide (H2S) (Cooney and others, 1999). The native sulfur was deposited from oxidizing hydrogen sulfide released by the bacteria.

The massive yellow and white chunk samples from site 2 are Tschermigite, in the sulfosalts category (Cepeda, 1994). The deposits are located on or adjacent to the fissure and are bulky rather then widely scattered. Since tschermigite is found only in Czechoslovakia, it is not initially part of the Centralia rock sequence. Tschermigite minerals have been noted around the world near volcanically active regions and other "hot spots". The presence of Tschermigite in bulky samples leads us to conclude that the samples are hydrothermally deposited from heated waters rising to the surface. "Sulfosalts occur primarily in hydrothermal ore deposits-deposits formed by the crystallization of elements concentrated and carried in a hot water solution produced as magma cooled or by water flowing through a hot fractured rock" (Cepeda, 1994). The coal fires burn very hot and heat groundwater to temperatures well above 100º C. The sulfur compounds dissolve into the solution and react with other ions present in the solution to form the deposit molecules. The deposits precipitate out of solution upon contact with the cool air at the surface. The presence of Tschermigite suggests that the coalmine fires of Centralia impose characteristics to the surface quite similar to other high temperature regions on earth, particularly volcanically active areas and "hot spots".

The apjohnite samples obtained from inside the vent at site 3 are also hydrothermally deposited. Apjohnite is usually white and found as a coating, which is characteristic of the samples we obtained. Because the apjohnite is coated over existing rocks rather then blocky monolithic forms, it is concluded that the apjohnite is deposited on the surface through the steam rather then rising waters as with tschermigite. As the hydrothermal solution reaches the surface, the apjohnite precipitates out of the gases and then deposited. This causes the sprayed, or coated effect. Apjohnite has a very similar chemical make-up as the tschermigite, suggesting that only slight differences exist between the two vents. The chemical compositions of the two minerals are shown in figure 2.

Figure 2
















N = 3.09 %

Mn = 6.18 %

The similar chemical components’ weight %’s of the two minerals are correlated to quantitatively evaluate the similarity. The correlation coefficient is an extremely high 0.999692, suggesting very strong correlation and close similarity. The correlation plot is shown as figure 3.



Figure 3


The difference between the tschermigite and apjohnite is the presence of nitrogen in tschermigite and manganese in the apjohnite. The two vents are a few hundred feet apart and may be running through slightly different bedrock altering possible ions that enter the solution. Also, the temperature of the ground at site 3 was much higher then at site 2. Different temperature waters have different solvent properties so what may dissolve in one hydrothermal solution may not dissolve in another. This may also explain the different modes of deposition for the two sites. If the groundwater at site 3 is much hotter then at site 2, the steam will escape faster and may distribute the precipitates in more of a spray fashion.

The "white crystal" from site 1 and the "red chunk" from site 2 are also believed to be hydrothermally deposited based on their depositional distribution and appearance. Both samples are located next to vents and are resting on moist ground. Unfortunately, strong conclusions could not be made because the X-ray diffraction analysis yielded no strong matches for these two samples. When the "red chunk" sample was tested, "chromium sulfate hydra" resulted with a pretty good match. We hypothesized that the red chunk samples would be similar to the tschermigite samples based on the relative locations of these samples and visual similarities. Neither tschermigite nor apjohnite show up in X-ray analysis of the red chunk samples. Further investigation of the red chunk samples is necessary to determine what the nature of this deposit is. A change may have occurred in the origin, transport, or deposition of these minerals. We have a few hypotheses: the deposits are from a different vent or are remains from a different time, the deposit has encountered a chromium rich chemical which has reacted with the mineral, the deposits molecules originate from a relatively small, chromium-rich inconsistency in the coal. Re-sampling, closer visual observations, and re-analysis of old and new samples are recommended to solve this problem. Analysis under different measurement such as chemical composition may reveal an answer as well, but not possible due to time restrictions. It is recommended in additional studies to run the X-ray diffraction analysis for these two samples for a longer duration, possibly an hour or two. Longer runs may yield better data for the "white crystal" and "red chunk" samples.


Centralia, a small town located in Columbia County, Pennsylvania, has been plagued by an underground mine fire in the Buck Mountain anthracite coal beds since 1962. In less then 40 years, 95% of the population has been relocated to neighboring areas by the government to an effort to avoid potential hazards such as noxious gases and subsidence.

Vents and fissures are scattered all throughout Centralia relieving the increased underground pressure caused by the fires. Sulfuric steam and smoke rise from these vents and different colored deposits surround the fissures. The deposits are collected and, via X-ray diffraction analysis, found to be either native sulfur or sulfur-bearing minerals, proving the hypothesis. The native sulfur is deposited on an anthracite sample from which the bacteria, Desulfovibrio desulfuricans, utilize carbon for energy to reduce the anhydrite and gypsum to hydrogen sulfide. The atmosphere oxidizes the hydrogen sulfide and native sulfur is formed. Apjohnite samples are found as a crust formed on the rocks through which a vent travels at site 3. The apjohnite crust coats the entire vent structure and is white with a slightly vesicular appearance. Apjohnite is deposited through precipitation from condensing steam that distributes the mineral as a coating over the vent. At site 2, tschermigite deposits are found as blocky masses right at the vent openings suggesting hydrothermal deposition from heated groundwater. Apjohnite and tschermigite samples have similar compositions with the chemical components wt. %’s correlating to 0.999692. This suggests that these samples are derived similar with possible slight differences in bedrock and/or solvent temperature. Tschermigite is usually only found around volcanically active areas displaying the similarity between Centralia and other "hot spot" areas. Centralia is not the largest coal fire in the world, yet the emotional and psychological stresses it has caused are unparalleled by any other underground fire. The Centralia mine fire could conceivably burn for another century. Unfortunately, the damage has already been done.

References Cited

  1. Alvarez, R., Clemente, C., and Gomez-Limon, D., Nov. 1997, Reduction of Thermal Coals Environmental Impact by Nitric Precombustion Desulfurization, Environmental Science and Technology, vol. 31, pp 3148-53.
  2. Barthelmy, D., May 1999, Mineralogy Database – Apjohnite Mineral Data, http://web.net/%/Edaba/Mineral/data/Apjohnite.html
  3. Barthelmy, D., May 1999, Mineralogy Database – Tschermigite Mineral Data, http://web.net/~daba/Mineral/data/Tschermigite.html
  4. Bell, P., and Wright, D., 1985, Rocks and Minerals, Macmillan Publishing Company, New York, pp 12, 347.
  5. Centralia Coal Company, 1999, Centralia Coal Company Homepage, http://www.centraliacoal.com.
  6. Cepeda, J. C., 1994, Introduction to Rocks and Minerals, Macmillan College Publishing Company, New York, pp 22, 28.
  7. Chinchon, J. S., Querol, X., and Fernandez-Turiel, J. L., Jul/Aug 1994, Environmental Impact of Mineral Transformations undergone during Coal Combustion, Environmental Geology and Water Sciences, vol. 18, pp 11-15.
  8. Cooney, M. J., Roschi, E., Marison, I. W., von Stockar, U., and Comninellis, C., 1996, Physiological Studies with the Sulfate-Reducing Bacterium Desulfovibrio Desulfuricans – Evaluation for Use in a Biofuel Cell, Enzyme and Microbial Technology, vol. 18, iss. 5, pp 358-365.
  9. Department of Environmental Protection, Feb. 1996, A Brief History of the Centralia Mine Fire (Borough of Centralia, Columbia County), http://www.dep.state.pa.us/dep/deputate/minres/BAMR/centbrf.htm
  10. Funk and Wagnall’s Encyclopedia, 1999, Anthracite, http://www.funkandwagnalls.com/encyclopedia/low/articles/a/a002000347f.html
  11. Glover, L., May 1998, Burning Beneath the Surface, http://www.penweb.org/issues/mining/tribrev/swfires.html.
  12. Glover, L., May 1998, Mine Fire Still Rages Beneath Tiny Town, http://www.penweb.org/issues/mining/tribrev/centralia.html.
  13. Hammond, C. R., 1974-1975, CRC Handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., pp B-31.
  14. Kittl, B., Oct. 1999, China’s on Fire, Discover Magazine, Walt Disney Company, New York, vol. 20, no. 10.
  15. Levin, H. L., 1996, The Earth Through Time fifth edition, Saunders College Publishing (Harcourt Brace College Publishers), Orlando, pp 324-341.
  16. Logue, J. N., Stroman, R. M., and Sivarajah, K., Jul/Aug 1991, The Centralia Mine Fire; An Overview of Community Health Surveillance Efforts, Journal of Environmental Health, vol. 54, pp 21-23.
  17. Lowenstern, J., 1999, USGS-Alid Volcanic Center in Eritrea, NW Africa, http://wrgis.wr.usgs.gov/lowenstern/alid/alidphotos.html
  18. Mottana, A., Crespi, R., and Liborio, G., 1978, Simon and Schusters Guide to Rocks and Minerals, Simon and Schuster Publishing Company, New York, pp 12, 347.