Anandakanda 2.7.102

2.7.102

<maṇḍūrabhasma>
lohakiṭṭaṃ sutaptaṃ ca yāvacchīryati tatsvayam /
tacchīrṇaṃ grāhayetpeṣyaṃ maṇḍūraṃ yaṃ prayojayet //

<Calcinated ash of maṇḍūra>
And the iron dross is heated well until it breaks down by itself; / one should take that which has broken down, grind it, and use that as maṇḍūra.