A blue pigment having the chemical stability of authentic Maya Blue can be prepared from indigo and attapulgite with the raw materials available to the ancient Maya, and by techniques presumably within their knowledge. The procedure possibly used consists of impregnating attapulgite with an extract of indigo plant leaves and stems and subsequently heating the impregnated clay for an extended period of time at the temperature of boiling water. This procedure would obviate the need for transportation of montmorillonite to areas far removed from its source and would account for the existence of the various types of Maya Blue noted in a previous report. (Analytical procedures are described in an earlier report. See 17-1349.) -- AATA