The term MAKEUP OF SOME SEAMS can be solved by the four-letter word COAL. COAL is a combustible black or brownish-black sedimentary rock, formed over millions of years from the remains of plants that were buried and exposed to intense heat and pressure. It is a fossil fuel, and is used as an energy source in many countries around the world. In terms of makeup of some seams, COAL is often used as a filler material to help strengthen and reinforce the seams.