Cleats are the vertical or nearly vertical sets of fractures in coal. Cleats often occur in orthogonal pairs and, when combined with bedding planes, cause most coals to have blocky fracture (Picture 1). The prominent or systematic cleat is called the "face cleat", whereas the less pronounced set is referred to as the "butt cleat" (Pictures 2 and 3). In plan view, the face cleat is generally linear to curvilinear and forms parallel to sub-parallel sets that can be regionally extensive. Butt cleats generally form parallel sets that are aligned normal to the face cleats. Additional sets of cleats can form. In addition, many variations to the general geometry occur (Pattison et al., 1996). Cleat surfaces are usually smooth, but also can be striated. Some cleat surfaces are slickensided or sheared indicating movement.
Figures & Tables
This volume of the “Atlas of Coal Geology” provides 393 images on various subject matters related to coal deposits and coal resource utilization. The supporting text provides an introductory overview of coal exploration, mining, and coalbed methane (CBM) development, followed by discussions on various megascopic aspects of coal geology (microscopic aspects are covered in Volume 2). Because of the vast subject matter, many generalities had to be made in the text. References are included to guide those interested to more detailed discussions. All citations within the document are linked to the detailed reference list for this volume. The overriding theme for this publication is that a picture is worth a thousand words.