Mr. Obama rarely plays with other politicians - though he has played 7 times with Vice President Biden. In a fence-mending gesture, Mr. Obama invited then-House Speaker John Boehner to play on one occasion in June 2011 along with Gov. John Kasich, both Ohio Republicans.
Here are some ways to classify coal (by grouping it with similar types of rocks): Because slag formed from lava-like melted rock, it's sort of like an igneous rock -- but because humans made the melt, it's not a true igneous rock. So, we made up a new classification for slag: We call it a pseudo-igneous rock (pronounced SUE-doe ig-NEE-us).
Some of the sulfur that exists in tiny specks in coal (called pyritic sulfur  because it is combined with iron to form iron pyrite, otherwise known as fool's gold) can be washed out of the coal in this manner.Typically, in one washing process, the coal chunks are fed into a large water-filled tank.imestone can be made to absorb sulfur gases under the right conditions much like a sponge absorbs water. In most scrubbers, limestone (or another similar material called lime) is mixed with water and sprayed into the coal combustion gases (called flue gases).