What exactly is "Eretz asher Lo be'Miskeinus Tochal bah Lechem" referring to?
What are the implication of "Eretz asher Avanehah Barzel u'me'Hararehah Tachtzov Nechoshes "?
Ramban: "Eretz asher Avanehah Barzel u'me'Hararehah Tachtzov Nechoshes". You will anticipate mining stones but you will discover that it is iron - to inform us that in Eretz Yisrael it is possible to mine iron and copper.
Ramban #2 (citing Targum Yerushalmi): "Eretz asher Avanehah Barzel" - refers to large stones, heavy stones and hewn (?) stones that are ideal for building houses, walls and towers.
Seforno: "Eretz asher (Avanehah Barzel) u'me'Hararehah Tachtzov Nechoshes" - And it also contains quality metals that are good for building and for manufacturing vessels,
Targum Yonasan: It refers to its Chachamim who issue decrees that are as firm as iron and its Talmidim ask questions that shine like copper.