Rasarnava 6.4

6.4

pinākaṃ darduraṃ nāgaṃ vajraṃ cābhraṃ caturvidham
pināke 'gniṃ praviṣṭe tu śabdaś ciṭiciṭir bhavet //

Pināka, dardura, nāga, and vajra: mica is of four kinds. / When pināka enters the fire, a crackling sound occurs;