Valmiki Ramayana Bala Kanda Sarga 37 Shloka 19

तत्र there, तैक्ष्ण्यात् from its severity, ताम्रम् copper, कार्ष्णायसम् चैव iron also, अभ्यजायत were produced, तस्य from that embryo, मलम् dirt, त्रपु zinc, सीसकमेव lead, अभवत् born, तत् एतत् that vital fluid, धरणीम् earth, प्राप्य having reached, नानाधातु: various minerals, अवर्धत developed.

There copper and iron were produced from its acidity, zinc and lead from its residue. Various minerals were formed when that embryo reached the earth.