The famous Papyrus Graecus Holmiensis has been digitized and is online at the World Digital Library here. Also known as the Stockholm Papyrus, this 4th century CE codex contains recipes for mordanting and dying imitation stones. For example, recipe 101 is as follows:
"Cold Dyeing for Purple which is Done in the True Way"
"Keep this as a secret matter because the purple has an extremely luster. Take scrum of woad from the dyer, and a sufficient portion of foreign askant of about the same weight as the scum – the scum is very light – and triturate it in the mortar. Thus dissolve the alkanet by grinding in the scum and it will give off its essence. Then take the brilliant color prepared by the dyer – if from kermis it is better, or else from kirmnos – heat, and put this liquor into half of the scum in the mortar. Then put the wool in and color it unmordanted and you will find it beyond all description."
It's nice to have all the papyrus leaves online and available for study. An English translation may be found in Caley, E. R., "The Stockholm Papyrus: An English Translation with Brief Notes,”Journal of Chemical Education IV:8 (1926): 979-1002, conveniently posted online here. The German edition is also online here. Be sure to check out the images of this fascinating codex!