The inert matter in coal

There are two categories of inert matter:
(a) (Moisture CONTENT and (b) MINERAL MATTER. Each has two divisions: INHERENT and

EXTRANEOUS. Thus there are four types in all:
INHERENT MOISTURE: part of the coal
EXTRANEOUS MOISTURE:
Free, mainly on the surface

INHERENT MINERAL MATTER: part of the coal
EXTRANEOUS MINERAL MATTER: Mainly shale, and separate from the coal