ddd111,
Not sure by what you mean "Bag of Aluminium Smelter"?? It would be hard to carry an Aluminium Smelter in a bag!
Do you mean Alumina?
Also you mention want to measure "qualitatively" the percentage of Al2O3 in your bag. That would be "quantitative" wouldn't it?
I would suggest you look at the ASTM methods for measuring Al2O3 content.