What is it? Ochres are natural clay earth pigments and one of the first pigments used by humans. Brown ochre (FeO(OH), is a partly hydrated iron oxide (goethite).
How is the pigment made? Grind the extracted clay into a fine powder and wash the impurities out.
Was it used in English manuscripts? Yes.
Is is safe? Yes. But always take care to wash hands after touching and avoid inhaling raw pigment.