Hello!

What Dresq said above is correct. You can only store up to a certain amount of each kind and the next time you get an Ore again, it'll not get added to your stack of Ores. Now, I feel like you will ask this sooner or later, about having the second stack of your Ores, that's from Recycling. If your Ores are already at maximum limit and you Recycled a Tool, that's the only time it will get added to your new stack.

Note: Correct me if I'm wrong because it's been a long time since I've done this Ore Mining thing and Recycling. Thank you.