The interpretation of regional magnetic anomalies commonly observed over continental crust in both satellites and near-surface magnetic data has remained enigmatic in its requirement for laterally extensive, thick, highly magnetic, and deep-seated sources. Presented here ar the results of a detailed field, analytical, and experimental study of the magnetic mineralogy and magnetic properties of rocks from Lofoten and Vester¿len, Norway, a province of deep-seated origin with associated regional magnetic and gravity anomalies. These rocks have a bulk magnetic character of surprising uniformity, with susceptibilities, hysteresis, and Curie temperatures defined solely by coarse-grained magnetite. Stable remanence is observed in samples from SW Lofoten but is not of significant magnitude. The thermal enhancement of magnetic susceptibility, the Hopkinson effect, is not important. Rocks from the deepest part of the section have the largest average susceptibilities, 6¿10-2 (SI), and magnitudes of natural remanent magnetization (NRM). 5¿10-4 A m2/kg. These values of susceptibility, together with the oft-observed viscous character of the NRM, suggest that these granulite facies lithologies (particularly those of SW Lofoten) are perfect examples of lower crustal sources of typical regional magnetic anomalies. Furthermore, these intermediate-pressure granulites define a unique magnetic petrology, especially for mafic compositions. At higher grades of metamorphism (high-pressure granulites and eclogites) or lower grades (greeschist and amphibolite facies) such magnetite-bearing assemblages will be unstable, and their high- or low-grade equivalents will be only weakly magnetic. This evidence and these conclusions may be used to constrain models of lower crustal sources of regional magnetic anomalies over stable cratons. It portrays the lower crust as a highly magnetic unit, defined by metamorphic grade, with a Curie isotherm of 575¿C (magnetite) and magnetization parallel to the ambient geomagnetic field (induced and viscous components).