There are no rare sats. If you spend a utxo it makes a separate one for the change.

To give an analogy it would be like spending a 20 bill for an item that costs 10. The store would get a new 10 dollar bill. The miner would get a new dollar bill and two new dimes. You would get a brand new 5 dollar bill, 4 brand new ones, and some other new coins. The original 20 bill would disappear.