MASTER-LOAD, in mining, a term used to express the larger vein of a metal, in places where there are several veins in the same hill. Thus it often happens, that there are seven, sometimes five, but more usually three veins or loads, parallel to each other, in the same hill. Of these the middle vein is always much the largest. This is called the master-load; and the others which lie three, two, or one on each side of this, are called the comcomitants of the master-load.