hydrated iron oxide? maybe it was clay in a fire.could have been war paint.I think its yellow before it gets heated if it is ochre.someone here will have a good answer for you sandman, im just an old hillbilly.
Good variety, sumpin small to shoot em with and sumpin large to skin em out
True ochre is clay with iron oxide content, color ranges from light yellow through red to dark brown.
BUT just for conversation real clay is usually very smooth all over, your example seems to be 'crinkly'
where it is broken. Might be a piece of limestone that has changed color with heat.