[Franklinite]The Illustrated London News, vol. 47, no. 1328, p. 142.
August 12, 1865
Franklinite is a black vitreo-metalloid substance, found in New Jersey. It is only slightly magnetic; is fused by the blowpipe with some difficulty, and its composition, according to Berthier, is--peroxide of iron, 66; red oxide of manganese, 16; and oxide of zinc, 17. Hitherto it has been merely an object for the cabinet. We now learn that, when it is combined with forged iron or steel, it gives excessive hardness, which no tools can penetrate, and which is not destroyed by the action of heat.