Burt discovered the Marquette Iron Range in Marquette County of the Upper Peninsula of Michigan in 1844. He worked closely with state geologist Dr. Douglass Houghton on iron ore samples. He took over his geological notes after his death in 1845 to complete the surveying work started. Burt noticed that the needle of a magnetic compass would spin violently in some locations in the vicinity. He persevered however, in his survey of the area using a solar compass he devised. He had realized the normal magnetic compass would not furnish accurate readings owing to the large iron ore deposits of the area. The compass needle was magnetized and would point in the direction of a large iron deposit, which generally was in a northerly direction. That idea was fine except where there were vast deposits of iron all around a local land territory. This was the case in the Upper Peninsula of Michigan, so the magnetic compass was completely useless there. The Great Lakes iron range that Burt discovered in his surveying work yielded 80 percent of the nation's ore production.