Coal has no fixed chemical formula and is therefore classified as sedimentary rock. The major elements of coal are silicon, calcium, aluminum, iron and magnesium while the minor elements are potassium, sodium, titanium, phosphorus, chlorine and manganese. Geologists estimate it took five to eight feet of peat to make one foot of coal. Coal deposits vary from a few inches to several hundred feet with most beds being 2.5 to eight feet in depth. Occasionally, the earth's crust buckled or folded and increased the pressure and heat beneath the surface. This increase of pressure formed higher grades or better quality of coal. Each grade of coal was rated by A being the best grade or quality in the category followed by B, C, etc.
There are four main classes of coal as follows:
1) Anthracite is the hardest coal and lies deepest in the earth. Most of it is found in Pennsylvania. It has the highest percent of carbon and the least percent of water causing no smoke when it burns, and therefore has less heating value.
2) Bituminous is soft coal, from the Cretaceous Period, and is half of the world's supply of coal.
3) Subbituminous is a softer coal, from the Tertiary or Late Cretaceous Period, and contains 25 percent water.
4) Lignite is the hardest type of brown coal containing 50 percent water, and is therefore a soft coal.
The government started analyzing the coal once it became a major
source of energy in the United States. They analyzed the moisture, volatile
matter, fixed carbon, ash, sulfur and British Thermal Units (BTU). Good
quality coal should have 12 to 16 percent moisture content. If the percent
is too low and the coal becomes wet, this can cause spontaneous combustion.
If the percent is higher than 16, it can lessen the BTU value. The British
Thermal Unit (BTU) is the ability the coal has to produce heat. The higher
the BTU is the better the coal quality. The fixed carbon rating is the
amount of carbon available for burning. The higher the rating is the better
the coal quality. The volatile matter is the gas and oil in the coal that
is available to burn. The higher the rating is the better the coal quality.
The ash content is how many ashes and clinkers are left after the coal
has burned. The less ash there is the better the coal quality. There should
be less than one percent sulfur in the coal because the sulfur when it
is burned produces the pollutant, sulfur dioxide. The lower the sulfur
content is the better the coal quality.
The Green River Coal Region is the largest in Wyoming with 16,800 square miles containing 237,110 million tons of coal. It contains sub-bituminous C to high volatile C bituminous. Bituminous and high ranking sub-bituminous coal moisture is less than 15%, volatile matter content is 30 to 40% and fixed carbon content is greater than 40%. The lower ranked sub-bituminous Tertiary coals have moisture at 20 to 30%, as well as volatile matter and fixed carbon. Ninety-nine percent of Wyoming's coal contains less than 1% sulfur, but the highest sulfur coal is in the Green River Coal Region. The Wasatch Formation coals not being mined have 7% sulfur. Western Wyoming coal heat values average 9,600 BTU/pounds and Wyoming's average is 12,000 BTU/pounds. Coal bearing rock in the Green River Region is largely concealed by younger rock and little is known about the total coal resources in the region particularly in the upper Green River Valley area. Coal beds occur in the Mesaverde and Lance formations of the Upper Cretaceous, the Fort Union of the Paleocene and Wasatch Formation of the Eocene age.
The Hams Fork Coal Region is the fifth largest in Wyoming with 49,160 million tons of coal. It is in the Overthrust Belt which is underlain by coal bearing rock from the Bear River Formation in the Lower Cretaceous and the Frontier, Blind Bull and Adaville formations in the Upper Cretaceous while the Evanston formation is in the Paleocene Age. The Overthrust Belt is part of a larger Tectonic Province of the Cordilleran Belt from northern Alaska to southern Mexico. The Cordilleran Fold Belt is divided longitudinally into at least nine segments or salients. The Idaho-Wyoming-Northern Utah salient is 200 miles long, arcuate, with an easterly convex belt of faulted and folded rocks bordered on the north by the Snake River Plain and on the south by the Uinta Uplift. The east is defined by Cliff Creek-Prospect-Darby Fault and the western boundary is the Wasatch Front. The Overthrust Belt is folded Paleozoic and rocks with the younger Cretaceous and Tertiary rocks of the area resting uncomfortably on top of these long, narrow belts bound by major thrust faults or eroded limbs of folds. The coal bearing rocks usually dip westward 16 to 80 degrees with an average of 25 to 30 degrees. The Blind Bull or Vail coal bed has high volatile bituminous coal up to 10.2 feet thick. Most mines mined six to 7.5 feet of low ash and sulfur coal beds ten miles long. The analysis of the coal shows 7.4% moisture, 39.4% volatile matter, 47.5% fixed carbon, 5.7% ash, .6% sulfure and 12,210 BTU/pounds.
The Jackson Hole Coal Field is 700 square miles with 6,340 million tons of coal. The coal occurs in the upper Cretaceous, Paleocene and Eocene age rocks. The coal is probably sub-bituminous. Teton county has mined 0.01 million tons of coals while Sublette County has mined 0.02 million tons.
Humans have mined coal for centuries. During the Bronze Age, 3,000 to 4,000 years ago, people of Glamorganshire, Wales used coal to burn their dead. The Chinese were using coal in 1100 B.C. while the Greeks used coal several hundred years before Christ. The Pueblo Indians used coal for their pottery making much earlier in the southwest than the white settlers used coal. Coal was first discovered by the white settlers in the United States during 1673, 80 miles southwest of Chicago along the Illinois River, but was not mined until the 1740's in Virginia. John C. Fremont found "alternating beds of coal and clay" just east of what became the Cumberland townsite in southwest Wyoming on August 19, 1843. In 1859, a coal mine was established three miles east of the old Bear River City as a Military Coal Reservation for the blacksmith at Fort Bridger.
There are several types of coal mines, but the type used in the Upper Green River Valley area is the Drift Mine. It is used to reach coal in hillsides. The main entrance is located where the coal is exposed and the tunnel is dug farther back into the bed of coal. "Shooting-of-the-solid" is coal being blasted off the solid bed without undercutting, or the mine face near the bottom of the coal bed is dug out so coal will fall down. A dangerously large explosive charge is needed and produces the dust and fine coal. Short holes are drilled at intervals along the face. The explosives are inserted in these holes. Black powder and dynamite were once used as chief explosives, but have a tendency to set fire to the gases and dust so they were discarded as too dangerous. Permissible powder replaced the black powder and dynamite and was approved by the U.S. Bureau of Mines, which is no longer in existence. Sometimes to make the mine safer by minimizing the possibility of the coal igniting, the mine was rockdusted by pulverizing limestone, a nonexplosive matter, so it could be sprayed on the roof, walls and floor of the mine. The tipple is where the coal is cleaned and sized. There are five sizes of coal which are lump, egg, nut, pea and slack. The lump is the largest ranging from the size of a man's fist to two or three feet in diameter. Egg is the next size and is about the size of any egg. Nut is the third size being the size of any shelled nut. Pea is the fourth size and it is the size of the vegetable pea. The smallest size is slack, which is tiny, fine pieces with a great deal of dust. The size of coal bought depends on what kind of heating unit the coal is going to be used in to produce heat.
The coal miners used carbide lights attached to their canvas and
leather miner caps in the beginning to see in the mines. They put carbide
in the light and water dripped on the dry carbide producing a gas which
could be ignited producing the light needed to see. After batteries were
developed in the 1940's, the miners used battery run lights attached to
their hard hats.
One old timer, Vince Guyette, called these mines "gopher-hole wagon mines." In the late 1800's and very early 1900"s, many of the mines were for anyone to use. An individual would go to a mine and dig his own coal. He did not have to pay for the coal, just use his muscles. As time went on and the mines developed, a small amount was charged by the mine owner such as in 1906, Julius Sayles, owner of Viola Coal Mine, was charging $1.50 to $2.00 per ton. For many of the ranchers, it was a long distance to the coal mine with a team and wagon. Many were 20 to 40 miles from the mine with some being as much as 50 miles away. The ranchers or business men who came for coal were fed a meal by the wife of the mine family, and many times they stayed the night before starting home with a load of coal. If they did not stay at the mine, they would spend the night with ranchers along the way. This all made the coal mines fit into the neighbor exchange system to survive along with helping a neighbor brand, gather cattle, build a house, or anything else that needed to be done so people in this very isolated, mountain valley could survive. The ranchers needed the coal to run their forges which kept the ranch operating. Many of the ranchers were 30 to 40 miles from town and 100 miles from a railroad, and therefore needed to be able to fix and build needed equipment.
As time went on people from the small communities in the area would pay for coal to be hauled to their home or business for heating fuel. When the oil boom in the 1900's took place around LaBarge and Big Piney, the coal was bought to heat the boilers fueling the rigs to drill for oil. As the oil and gas industry developed, it replaced coal as the energy source. The mines eventually closed when oil and gas replaced coal as the main energy source. Furthermore, when the highways were built, it was easier to go to Rock Springs for coal rather than to isolated mines with rough, dirt roads accessing them.
According to Gardner, Johnson and Allen in The Twitchell Mine:
A Historical Overview, the following four factors influenced the growth
and development of the wagon mines:
1) The lower elevations of Wyoming had little wood, but had an abundance of coal for fuel.
2) There was little "hard cash" in the late 1800's and early 1900"s and it took only hard work to get the coal. Few people filed on mining claims so to not have to pay Uncle Sam.
3) Homesteads were a long way from the railroad where coal could be obtained readily.
4) Ambitious ranchers who wanted more income would develop a coal mine.