A sedimentary intrusion is a variably shaped, discordant body of sedimentary rock which disrupts coal-bearing strata (Pictures 1, 2, 3, and 4). Sedimentary intrusions can vary in lithology, have significantly different modes of emplacement, and in many cases resemble their igneous counterparts (Picture 5) (see Depositional Systems, Volume 1). For purposes of this report, sedimentary intrusions are categorized as follows: 1) sedimentary dikes, sills, and pipes which also are referred to as rock spars, clastic dikes, sandstone dikes, stone dikes and etc.; 2) clay veins which also are referred to as clay dikes, clay slips, horsebacks, mud slips, and etc.; and 3) sediment infilling of fractures. Because intrusions are often composed of hard rock and disrupt the coal seam, they can impact both coal mining and CBM production. In extreme cases, sedimentary intrusions can be so prolific that coal mining in those areas is not economical.