I would call this a classic yellow ochre, sourced from Italy, you are yet again seeing the integrity of Rublev, this is the finest source of these pigments, not the easiest or the cheapest but the best, there is a good chance Caravaggio was grinding this very same 'earth' several hundred years ago.
It is a semi- transparent deep golden yellow with good tinting strength, medium grained that makes pale biege half tints.
Hydrated iron oxide is the principle coloring agent in yellow earths. This color is based on the natural mineral goethite associated with varying proportions of others minerals such as clay, chalk and silica. They differ from other ochres in that they contain water. In other words, the iron to which they owe their colour is hydrated iron oxide.
|Colour Index:||Pigment Yellow 43|
|Chemical Name:||Natural Hydrated Iron Oxide|
|Chemical Formula:||Fe2O3 � H2O|