Jamieson, Fausset and Brown on Deuteronomy 8:9

9. a land whose stones are iron--The abundance of this metal in Palestine, especially among the mountains of Lebanon, those of Kesraoun, and elsewhere, is attested not only by Josephus, but by Volney, Buckingham, and other travellers.

brass--not the alloy brass, but the ore of copper. Although the mines may now be exhausted or neglected, they yielded plenty of those metals anciently (1Ch 22:3; 29:2-7; Is 60:17).