charbon mat

OBS: Ce peut être soit du durain, soit un charbon à forte teneur en matières minérales.

OBS: An early division was into three types: bright coal, dull coal and mineral charcoal (or mother of coal). Another system [divided coal into] four types: fusain, durain, clarain, and vitrain. This coincided with the classification put forward by ... the United States Bureau of Mines where coal is divided into anthraxylon - bright layers of plant material and attrius - darker debris material. Today coal classification is based on the organic material seen using different optical microscopic techniques. There are three main groups: liptinite (or exinite), vitrinite and inertinite with many further divisions [within these three groups].