Coal balls commonly contain dolomites, aragonite, and masses of organic matter at various stages of decomposition.[10] Hooker and Binney analysed a coal ball and found "a lack of coniferous wood ... and fronds of ferns" and noted that the discovered plant matter "appear[ed] to [have been arranged] just as they fell from the plants that produced them".[26] Coal balls usually do not preserve the leaves of plants.[27]