Block coals (CO-01)
Probably the two best known but less abundant coalbeds in Indiana are the Upper and Lower Block coals. They occur in seams 20 to 30 feet apart and are best developed in Clay County and southern Parke County, but they also occur in Owen, Greene, and Daviess Counties. Because these coals have natural fractures that cause them to split into cubes, early miners using handtools could wedge and break out the coal in blocks that ranged from a half a foot to 2 feet on a side. So these coals became known as "Block coals", a name that is still used despite the change to modern surface mining.

Block coals are among the highest quality coals in Indiana. They produce high heat values, leave a small amount of ash, tend not to form clinkers, and liberate only small amounts of sulfur dioxide pollutant when burned. Their high quality has made them sought after since the 1850's for domestic use, for the brick and tile industry, and for electric generating.

Our Hoosier State Beneath Us: Coal