Anandakanda 2.4.6

2.4.6

rūkṣāṅgaṃ sadalaṃ tāmraṃ neṣyate rasakarmaṇi /
utkledamohabhramadāhabhedāḥ tāmrasya doṣāḥ khalu durdharāste /
viśodhanāt tadvigatasvadoṣaṃ sudhāsamaṃ syādrasavīryapāke //

rough-surfaced, and flaky copper is not desired in alchemical work. / Nausea, delusion, dizziness, burning sensation, and diarrhea are indeed the severe defects of copper; / through purification, when its defects are removed, it becomes equal to ambrosia in the cooking of mercurial potency.