Here's why:

* Organic: Coal is formed from the remains of ancient plants, primarily trees, that accumulated in swampy environments.

* Sedimentary: Coal forms through the accumulation and compaction of organic matter over time.

While coal is classified as a sedimentary rock, it's not the same as rocks like sandstone or limestone which are made up of mineral fragments. Coal's unique composition and origin make it a special type of sedimentary rock.