OK here's another idea. weigh out, on a gram scale, a small container,a (soda)cap full level to the top of red iron oxide, then the unknown material. If it's red lead,it's likely to weigh far more in comparison to RIO. if it weighs almost the same, the difference is accounted for in the way the materials were placed in the cap
If you compare several different materials, say zinc oxide or strontium carbonate to silica or whiting or feldspar, you'll sone notice the relative weight of different materials.
Another idea, place a small amt of the red material on a sheet of paper and put a magnet under the paper and see if any or all the red oxide is attracted to the magnet