Currently with the way mining is, more than likely the miner's inventory is completely full of rocks ~99% of the time, and thus this leads to gems being dropped on the ground covered by the rock sprite.
When you first mine out that gem, size, and cut you will get a discovery notification. However, you will never know you mined that same exact gem again and its fairly easy to miss mining them.
The current meta in countering this is to always carry a gem on you and every so often in the area, drop the gem and Shift+RightClick that gem and it will autopath and pick up any gems in the area.
My proposed change is a fast visual shine or bright spark happens on the pickaxe when a gem is mined out.
Let me know thoughts, i think the current way could be improved for better gameplay and experience.