Rasahridayatantra 4.9

4.9.1

muñcati satvaṃ dhmātas tṛṇasāravikārakair ghanaḥ svinnaḥ /
parihṛtya kācakiṭṭaṃ grāhyaṃ sāraṃ prayatnena //

Steamed with the juice of grasses and their modifications, mica yields metallic essence when blown upon;
having discarded the glassy dross, one must zealously extract the pure essence.