How can I positively prove or disprove whether or not a solution is CaSO4 or Al(SO4)2.?

Question

I've narrowed down my mystery chemical in my chem lab to these two things (to a good degree of certainty). How can I confirm or deny either one of them?

Answer 1

Find the location of each metallic ion on the activity series. Add a solid metal that is higher on the activity series than Al but lower than Ca. The metal will replace Al in the solution.

Try using a solution which contains an anion which will combine with either Al or the Ca and form a ppt.

Answer 2

If it is highly soluble in water then it should be Al(SO4)2, and if not, Ca(SO4)2.

Answer 3

caso4 is white and AI(so4)2 is canary yellow in colour if this helps