Hastings' Dictionary of the Bible (1898)
I'RON. Prov 27:17. Some of the uses of this well-known and most valuable metal were probably understood at a very early period. Gen 4:22. We find it mentioned as the material for tools, Deut 27:5; 2 Kgs 6:6; weapons of war. 1 Sam 17:7; furniture, Deut 3:11; implements of husbandry, 2 Sam. 12:31: Jer 28:14; and chariots of war. Josh 17:16, etc. By "northern iron," Jer 15:12, probably is intended a species of iron-ore or manufacture remarkable for its hardness, found in a region bordering on the Euxine Sea, and of course north of Judaea.
The expression "a land whose stones are iron," Deut 8:9, seems to describe an abundance of iron-ore, which is certainly true of the northern parts of Palestine, as shown by recent exploration. See Steel.