Use of existing technology for coal extraction would not be profitable any more.

As an important center for coal extraction, the city was made a rayon center in 1936.

The complex geology and narrow seams made coal extraction difficult.

This is more than half of Brazil's total annual coal extraction.

At the height of coal extraction in the valley, there were several deep pits and numerous levels.

The earliest industry in the area was salt production, followed by iron production and coal extraction.

Each of these four largest coal-extracting countries are experiencing significant increases in coal extraction.

The slack has been taken up by large increases in subbituminous coal extraction.

Germany hit peak hard coal extraction in 1958 at 150 million tons.

In 2005 hard coal extraction was around 25 million tons.