Peat as a Type of Coal

Like the hydrogen sulphide question (see above), this one raised a few eyebrows. Is peat a variety of coal?

According to (the Encyclopedia) Britannica, "The formation of peat is the first step in the formation of coal. With increasing depth of burial and increasing temperature, peat deposits are gradually changed to lignite. With increased time and higher temperatures, these low-rank coals are gradually converted to subbituminous and bituminous coal and under certain conditions to anthracite."

Wikipedia agrees: "the formation of peat is often the first step in the geological formation of other fossil fuels such as coal, particularly low-grade coal such as lignite." The italics are mine: coal is a different fossil fuel from peat. In other words, peat is not a variety of coal.

If you google "peat coal", one of the results is geology.com, which gives peat as the first entry in its table summarising the "basic progression" in the "rank" of coal. "Peat", it says, "is an organic sediment. Burial, compaction, and coalification will transform it into coal, a rock."

(The "rank" of a coal is "a measure of how much change has occurred [in the composition of plant debris]".)

So peat is an organic sediment, and coal is a rock. This confirms that (according to geology.com) peat is not a type of coal – even though it is, by common consensus, "the first step in the formation of coal".

But there's more. The next entry in geology.com's table is lignite, which it describes as "the lowest rank of coal". It also says that lignite "sometimes contains recognizable plant structures".

In other words, the best answer to this question is "lignite". (In case you'd forgotten, the question was, "Which variety of coal contains recognisable traces of the original plant material?")

Geology.com also has a picture of some peat, whose associated text is "Peat coal".

I wonder what our former Secretary would have made of all this. Somehow, I think he might have heard it all before.

(For the benefit of those who didn't know him, the former Secretary of Macclesfield Quiz League was Pete(r) Cole.)