I don’t know what kind, specifically. Ochre covers a wide range of natural earth pigments with different compositions, but usually iron-rich.
I dig this stuff out of cracks in the Canadian Shield for paint pigments. It’s naturally colourfast and very close to, if not a little less pure than what’s used in commercial paint.
Just realized I forgot to answer your question. I either use acrylic medium or I make a watercolour mix with gum arabic as the binder.