Bill Tindall, E.Tn.
Dana compilation 1949. Disclosed in Am Min. Rec. 1958. Without reading the publication I don't know if the iron content is critical to the crystal structure or considered an impurity in a Cr3O3 crystal structure, that is to say, is the mineral Cr2O3, or a mineral that both Fe and Cr are essential to forming.

I have no idea when the green sticks began to be sold/used by woodworkers. I bought mine decades ago and used it on leather, and still do, for knives. All the carvers I know use it on carving tools. I needed a bit of "rice" carving and lacked the tool. Before it was loaned its owner, a Period Furniture maker, gave it a few strokes on leather/green stick.