Jigucchitabbasutta 2.6

2.6

seyyathāpi, bhikkhave, tindukālātaṃ kaṭṭhena vā kaṭhalāya vā ghaṭṭitaṃ bhiyyoso mattāya cicciṭāyati ciṭiciṭāyati;

They’re like a firebrand of pale-moon ebony, which, when you hit it with a stick or a stone, sizzles and crackles even more.