Mercerized Cotton - How to tell?

If something is 100% cotton and is superiorly soft compared to similar items that are 100% cotton and are course is it generally safe to consider it mercenized? What if it does not appear to have a luster? I always have heard that that is the trademark of mercerized cotton but looking online not all seem to be full of luster. Are there any other processes which would make the cotton really soft without being mercerized? Thanks!