Nice collection there LW! :Y:
Gemhunter, sapphires and rubies are much harder than zircons or garnets. Harder than most things really. If you're not too worried about marking the surface a little, a stone that you know to be say, a zircon should have a great deal of difficulty making a scratch on the suspected sapphire/ruby, while a sapphire/ruby will easily scratch a zircon or garnet.
There may also be telltale signs visible under magnifaction, such as "sergeant stripes", which are rays of "silk" (tiny rutile crystals) which can give away the crystal shape. Sapphire and ruby crystals have a crystal shape that is hexagonal in cross-section.