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).
The inside of the earth is very hot - hot enough to melt rocks. The deeper you get the hotter it gets. Below the surface, the molten rock is called magma; at the earth's surface it becomes lava, nothing has changed only the name of the liquid. Igneous rock is made by fire. Small wonder the magma from which igneous rock is formed can reach temperatures close to 1200 degrees Celsius.