Anandakanda 1.26.186

1.26.186

kūpīpāṣāṇasaṃyuktā vajramūṣā prakīrtitā /
<mūṣāvaṅkanālakoṣṭhikopayuktamṛllakṣaṇam>
kṛṣṇā raktā ca pītā ca śuklavarṇā ca mṛttikā //

combined with glass stone: [this] is proclaimed as a vajra crucible.
<Characteristics of clay suitable for crucibles, bent tubes, and furnaces>
Clay is black, red, yellow,
and white in color.