coal-seam

n layer of coal under the ground 煤层.

co-respondent, corespondent, co-signatory, cosignatory, co-star, co-tenant, coach, coachman, coachwork, coagulant, coagulate, coagulation, coal, coal gas, coal oil, coal tar, coal-black, coal-face (also face), coal-hole, coal-mine (also pit), coal-miner, coal-scuttle (also scuttle), coalesce, coalescence, coalfield, coalition, coaming, coarse, coarse fish, coarse fishing, coarsely, coarsen, coarseness, coast, coastal, coaster, coastguard, coastline, coat, coat of arms (also arms), coat of mail, coat-hanger,