I ripped out some old wood windows in a rental house. THe addition was put on in 1950 but they used a lot of salvage materials - windowsprobably were much older. I threw the cast (iron?) counter weights (approx. 2 in. dia x 10 in. long) onto my scrap cast iron pile for a future trip the the metal recycler. As I was loading up the trailer with scrap one evening this week I decided to try to turn on of the counter weights - maybe I could find a future use (rather than giving it away for a couple of cents/ pound) for what I assumed to be cast iron. Using carbide, both C2 & C5, I was only able to cut thru the outer, rusty layer (in a cloud of dust, no chips!). Beyond that the carbide was simply polishing the material. What gives? What kind of a ferrous material is this?