Mineral Stain in Hard Maples and Other Hardwoods

Both the heartwood and the sapwood of living hard maple trees, and to some extent of other hardwoods, of the Lake States and northeastern forests commonly are disfigured by deep olive or greenish black discolorations generally known as mineral stain or mineral streak. These may appear on sawed materials as individual lenticular streaks of various lengths paralleling the grain or as mass discolorations. On specimens observed the latter form has been more prevalent in or near the heartwood. During seasoning both the streaked and the mass-stained wood have a pronounced tendency to crack open along areas where the discoloration is deepest. The defect is an important factor in the utilization of species affected. It not only results in serious degrade but, because of its variable occurrence, often within comparatively limited areas, also tends to be a source of objectionable error in stumpage evaluations.