Final answer:
Pyrite is found in coal deposits due to the sulfur-rich conditions of the environments, like ancient sea-covered swamps, where coal was formed. As these ancient seas dried up, sulfur was left behind and led to the formation of pyrite within the coal.
Step-by-step explanation:
There is a significant presence of pyrite in coal deposits because of the geological conditions under which coal forms. Coal originates from the accumulation and transformation of plant matter in environments such as swamps and bogs, where it is subjected to heat and compressive forces over millions of years.
In certain cases, such as in regions previously covered by sea water, the presence of sulfur in sea water contributes to the formation of pyrite.
As the sea water evaporates or the seas recede, sulfur can become trapped within the coal. This sulfur-rich environment leads to the formation of pyrite, or FeS2, due to the combination of sulfur and iron under suitable conditions.
Pyrite, a yellow mineral with a metallic luster, is commonly referred to as Fool's Gold due to its gold-like appearance. Bituminous coal, the most abundant type of coal found in the United States, is known to have a high sulfur content largely because of the small particles of pyrite contained within it.
The presence of pyrite in coal is of great concern because when coal is burned, the sulfur is released as sulfur dioxide (SO2), contributing to environmental issues such as acid rain.