system
Given the following post, respond as if you're commenting on Reddit:
human
I've always been told that coal takes millions of years to form. At what point does something like peat go from being called peat to coal, is there an inbetween?
gpt
Lignite, is a soft brown combustible sedimentary rock formed from naturally compressed peat. It is considered the lowest rank of coal

Since peat turns into lignite over geological period of time, there is no specific date at which one would point to say it's done...the cutoff between peat and lignite is not sharp
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