M.D.
Iron ore was available in the South. Virginia had been a major producer since Colonial times and other States went into production as the years went by, as this map shows:
http://www.virginiaplaces.org/geology/iron.html
However, the Confederate government had to seriously prioritize "War Materials" during the WBTS. So much of the Iron went into producing Rifle Muskets, Locks and Barrels even for the Bronze Framed Revolvers, as well as other items.
So, since Iron was a high priority material. If something was normally made from steel, but could be made from Iron, they did so. If something could be made from Bronze (like Revolver frames) they did so to conserve Iron. If something was normally made from bronze they often made it from brass, except for gun/cannon barrels, of course. Even when they made things from Brass, they often had a higher content of copper in the copper to zinc ratio than normal, to save on zinc. For example, Confederate Sword belt hooks are rather easy to identify vs Federal ones because the Confederate Hooks have a definite "reddish" hue to them and are normally cast rather than made into wire. Many Confederate made Waist Belt Plates and Frames also show this "reddish hue." That way they saved on zinc for other uses.
For those interested in the difference between Brass and Bronze, the following is a good link:
http://www.differencebetween.com/difference-between-brass-and-vs-bronze/
Now, Confederate prioritization of materials did not just include metals, but included all War Materials. Some examples are the Federals specified "Cashmere" wool for uniforms, which meant pure wool in the period, but Confederate Uniforms were often made of a wool and cotton and sometimes wool and linen blends.
Instead of making Cartridge Box slings and Rifle Slings entirely out of leather, they sometimes/often used woven linen/cotton straps and on rifle musket slings, used linen/cotton straps with small pieces of leather sewn on where the hooks went into holes for adjustment.
Gus