HOW DO WE KNOW THAT COAL WAS DERIVED FROM PLANT MATERIALS?
Although plant impressions or fossilized wood can be seen in coal, they are more common in shales and sandstones associated with the coal. Often roots can be seen in the clay that lies just under the coal, and in some places stumps of trees from the coal swamp forest are preserved in the sediments adjacent to the coal ([fig. 10]). When pieces of coal are examined with a microscope, carbonized plant remains can be seen.