Marl Lake: Polygorskite

At the same time that I am creating my indigo pigment I thought I should also get things underway in purifying the Marl I collected. What I really want to have from that Marl is a clay-ish mineral called Polygorskite. The other part of this marl is calcium carbonate which I can dissolve quite easily using a bit of hydrochloric acid.

So, putting some clean marl into a bucket I began to add the acid a little at a time. This resulted in lots of foam initially, but little by little it subsided. In the end what was left over wasn’t nice and white but a middle grey colour! Still I have no doubt that this is the polygorskite I wanted as this colour is known to exist for the mineral and it has a leather feel that is characteristic.

It will be very interesting to see what effect this deeper shade has on the final Maya Blue!