I notice at vendors :

petty soul gem (petty) and petty soul gem. What is the difference. One of them I can't seem to use for enchanting.

Also, if I give a wep to my follower that refills a soul gem if the enemy dies within n seconds, and give him soul gems..will that refill them?

One may be filled with a soul already and one may be empty. It will state this under the description and price. You can't use an empty soul gem to enchant, you must fill it with a soul first.

Not sure if followers can fill soul gems or not. It's a great question!

The first has a soul in it and the second is empty. A soul gem must be filled to use.

Yes.

Makes sense. I will double check the descriptions. Thanks.

The one with brackets is already filled with a soul.

Yep. Tested the follower filling them, it works great actually.

thanks