The Nature and Origin of Fusain

Abstract

Fusain, called also mineral charcoal, fossil charcoal, mother-of-coal, fusit, fusaine, and Faserkohle, has been known and variously interpreted since the early days of geology. Of the many early hypotheses concerning its nature and origin, three still have adherents. According to the first, known as the hypothesis, fusain is the product of the well known process of fungal decay known as dry-rot. Against this, it may be argued that dry-rot does not produce anything resembling fusain, and that fusain rarely if ever shows the least sign of the decay which attends dry-rot, but on the contrary is generally exquisitely preserved. The second or acid hypothesis postulates that fusain is derived from woody debris that lay at the surface of a swamp during times of evaporation, at which times the woody matter is supposed to have become impregnated and encrusted with concentrated humic solutions. These insoluble and poisonous humic concentrates, upon drying, might have hardened and protected the wood from further decay. Under the conditions postulated, however, no product resembling fusain, that is, having among other characters a pure carbon composition, is ever formed in modern swamps or bogs. Moreover, fusain is a stratified clastic sediment commonly occurring in thin even layers; quite the reverse of the highly irregular, hummocky, residual deposit which the hypothesis would lead one to expect. The third or charcoal hypothesis postulates that fusain is vegetable matter carbonized by fire. A number of objections have been made to this hypotheis but all of them seem to be readily answerable.