During a mapping project in the Colorado Plateau, a geologist described a mineral from a sandstone outcrop as metallic and hard, based on its shiny luster and dark surface color. Laboratory analysis showed the sample was soft, nonmetallic, and left a pale streak on porcelain. The research team revisited the original field notes to evaluate what observational reasoning had led to the misclassification. What explanation best accounts for the error in the geologist’s field interpretation?