कालायसस्यार्धभागाभ्यक्तं कृष्णं भवति ॥ कZ_०२.१३.५५ ॥
kālāyasasyārdhabhāgābhyaktaṃ kṛṣṇaṃ bhavati
Lorsqu’on l’enduit/le traite avec une demi-part de fer noir (kālāyasa), il devient noir.
Surface treatments can disguise base metals; state knowledge of such methods supports enforcement against fraud in bullion, ornaments, and coin-like pieces.