The association of columbite is with granitic, pegmatitic, and metamorphic rocks, and its occurrence is to be expected in southeastern Pennsylvania, where such rocks are well developed. The following localities have, in fact, been noted in this region:1 In Delaware County: Ridley township, quarry southeast of Avondale, on the east bank of Crum Creek, in granite gneiss; Springfield Township, quarry ½ km. (⅜ mile) northwest of Morton Station, also in granite gneiss; Middletown township, two localities, in pegmatite (exact locations not recorded); Middletown Township, Mineral Hill, 2 km. (1¼ miles) west of Media, between Ridley Creek and Black Horse, in pegmatite; and Upper Chichester Township, about 0.8 km. (½ mile) southwest of Boothwyn station, in pegmatite. In Chester County: London Britain Township, 1.6 km. (1 mile) southeast of Landenberg, east of the East Branch of White Clay Creek, where the country rock is crystalline limestone, but the matrix of the columbite uncertain. In Philadelphia County (City of philadelphia): southwest corner of Broad Street and Olney Avenue, in pegmatite.