My next step in creating a good Mars pigment involves changing the iron ore into iron sulphate (or Green Vitriol). There are a lot of different ways this can be done, but a simple method is to put the iron sample into some dilute sulfuric acid.
The reaction is quite something. The iron bubbles, and in fact the whole mixture begins to fizz like a soda-pop. In watching this I also realized one of the benefits of creating a bloom of iron: The acid could break down such a porous lump of iron much more quickly.
By this evening, all the iron had dissolved leaving a green liquid behind.