Some interesting stuff regarding metals in pre-Semitic Horn of Africa:
"Some solutions can be decisively discounted. The first Ethiosemitic speakers did not come as technologically advantaged conquerors. It may perhaps be possible that the South Arabian settlers introduced iron to the Horn. But what little as has yet been investigated of northeastern African iron-working terminology suggests that metallurgy in some form was already known and that the root * bir-t- used for “iron” throughout the Horn today was borrowed into early Ethiosemitic from a Cushitic source."
- History and Testimony of Language Christopher Ehret
"Quite possibly the migration of the Sahara pastoralists reached the Horn and East Africa. Settlements of village farmers, basically neolithic but also using some copper, are known from the plateau of north-western Ethiopia; their material culture shows affinities with that of the C-Group peoples who moved into Nubia from the western desert about 2500 BC......
- Jean Hiernaux
So it seems metallurgy was at least known in the Horn before the Semites came seeing as they had a Cushitic word for Iron but the lack of Iron thats been excavated must mean these Cushites either had an aversion/taboo towards metallurgy as is common in the Horn today and among Tuaregs who've absorbed Egyptian/Nubian ancestry indicating our metallurgy taboos may have a common ancient origin in Sudan/Egypt, or they were just incapable of producing metal(68iq)
"Some solutions can be decisively discounted. The first Ethiosemitic speakers did not come as technologically advantaged conquerors. It may perhaps be possible that the South Arabian settlers introduced iron to the Horn. But what little as has yet been investigated of northeastern African iron-working terminology suggests that metallurgy in some form was already known and that the root * bir-t- used for “iron” throughout the Horn today was borrowed into early Ethiosemitic from a Cushitic source."
- History and Testimony of Language Christopher Ehret
"Quite possibly the migration of the Sahara pastoralists reached the Horn and East Africa. Settlements of village farmers, basically neolithic but also using some copper, are known from the plateau of north-western Ethiopia; their material culture shows affinities with that of the C-Group peoples who moved into Nubia from the western desert about 2500 BC......
- Jean Hiernaux
So it seems metallurgy was at least known in the Horn before the Semites came seeing as they had a Cushitic word for Iron but the lack of Iron thats been excavated must mean these Cushites either had an aversion/taboo towards metallurgy as is common in the Horn today and among Tuaregs who've absorbed Egyptian/Nubian ancestry indicating our metallurgy taboos may have a common ancient origin in Sudan/Egypt, or they were just incapable of producing metal(68iq)