The Gem Shrine did not upgrade the 1 gem left in my inventory.
Instead the Gem Shrine only gave me an additional random Chipped Gem of a different color.
Arrived at 1st Gem Shrine (A4, Normal) with 2 gems in my inventory; a regular Topaz (lvl 12), and a Flawed Ruby. Removed the Ruby from inventory only, and then hit the shrine. I received a Chipped Sapphire in my inventory. It should have upgrade my Topaz to a Flawless Topaz.
Not exactly game breaking, but thought you should know.
Were the gems in your cube?
supposedly they do upgrade. i’ve never had a gem in my inventory when hitting one though, so i’ve never seen this in action.
but all the info sites for d2 going way back have mentioned it as a thing for some time (if not the beginning).
farming them has been a thing forever as well. start with one, and just run act1 start to finish. ignoring the mobs and just flat out run the whole act overmap. supposedly you can get an average of 2.5 games/gem shrine. plenty of pgems/day if you do nothing but grind out just a1. at a high enough level, most chars can do it in a couple of minutes or so/run.
good way to get crafting pgems. just make sure the one you want to be a pgem is the only one in your inventory at the time you click on the shrine. upgrade it at shrines till you hit top end. rinse, repeat.