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Crushed stone has one of the lowest average by weight values of all mineral commodities. The average unit price increased from US$1.58 per metric ton, f.o.b. plant, in 1970 to US$4.39 in 1990. However, the unit price in constant 1982 dollars fluctuated between US$3.48 and US$3.91 per metric ton for the same period.
The Powder River Basin mines supply approximately 40% of the coal that fuels those stations (mainly east of the Rocky Mountains) for generating electricity. [11] The mines work in areas where the stripping ratio is between 1:1 (i.e. one ton of rock for one ton of coal) and 3:1. [12] As the mines expand the stripping ratio will increase.
River gravel is a name given to gravel composed of small pieces of rounded stone of various colors, usually no larger than a large coin. [1] It is named for the effect of many years of rounding of the edges of the stones due to a flow of water over it, as often takes place in a river . [ 2 ]
The exact phosphate content of the phosphate rock mined in 2015 is not available, but in the latest five-year period for which ore grades are available, 2009-2013, the grade of US phosphate rock varied from 28.5 to 29.0 percent P 2 O 5. As of 2016, remaining reserves of phosphate rock in the United States totaled 1.1 billion metric tons. [1]
Btu per hour (Btu/h) is sometimes used in North America and the United Kingdom - the latter for air conditioning mainly, though "Btu/h" is sometimes abbreviated to just "Btu". [18] MBH—thousands of Btu per hour—is also common. [19] 1 W is approximately 3.412142 Btu/h [20] 1,000 Btu/h is approximately 0.2931 kW; 1 hp is approximately 2,544 Btu/h
The primary reason for the switch from wood to coal was one of economics. In 1809, a cord of wood cost $2.00 and a bushel of coal cost $0.06, delivered. The coal was plentiful and laborers, working in mines within a mile of Pittsburgh, earned about $1.60 per week and could produce as many as 100 bushels of coal daily. [22]
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Price per million BTU of oil and natural gas in the US, 1998-2015. Natural gas prices, as with other commodity prices, are mainly driven by supply and demand fundamentals. However, natural gas prices may also be linked to the price of crude oil and petroleum products, especially in continental Europe.