Cannel coal is a variant of mat coal (liptinite) that is a part of the strip-shaped coal seam in addition to bright coal (vitrinite) and fibre coal (fusite). As cannel coal is very tough and homogeneous, it is very easy to carve, grind and polish. After polishing, it exhibits a deep black gloss, which made it very suitable for use as jewellery. Cannel coal pieces were also purchased by gem cutters from Idar-Oberstein, which processed them into high-quality items of jewellery. This coal was often used to make mourning ornaments. The miners themselves also processed the widely available "carving coal". The cannel coal pieces were carved and filed into smaller pieces before being put into a preserving jar filled with water and sifted sand. After some shaking, the surface became smooth and names or symbols could be carved into it.