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).
BackgroundBurning coal produces a variety of solid wastes known as coal combustion waste or coal combustion products. These include coal ash (fly ash and bottom ash), boiler slag, and flue-gas desulphurization products.urning coal produces a variety of solid wastes known as coal combustion waste or coal combustion products.