This technical report presents the observations made during a study into cleat and joint directions,
largely in the Pennine Basin. Field work was carried out under the BGS Research and Development
programme in 199 1 - 1992. Interpretation of these observations will be made elsewhere.
Cleat is the term widely in use to describe joints in coals. It is generally developed perpendicular to
the bedding and there is normally one dominant set, known as the main cleat and a subsidiary, more
or less perpendicular, set known as the back or butt cleat. Other sets may be developed in places,
particularly in strongly faulted areas (see Figures 1, 2 and 3). Cleat is developed in all bright coals,
including coalified allochthonous plant fragments and reworked clasts
