How does the new salvaging of jewelry work?

I know the range is 5-10 for ilvl 50 and 5-15 for ilvl 51, but I was salvaging some jewelry the the other day and was getting 4 dust in some cases, which tells me there's a skill factor to it. How much of what skill do I need to achieve 5-10 and 5-15?

Thanks for this forum, by the way. I didn't realize it existed. What a cool thing.