The Pickonimbus 2000 is a reference to the Nimbus 2000 broomstick from the Harry Potter franchise.
This is the only pickaxe to have durability.
The pickaxe does not have a durability bar even though it breaks after 5,000 uses, instead, the number of uses left is displayed in the lore.
A Pickonimbus can be repaired to full durability in an Anvil by placing a brand new unenchanted Pickonimbus in the first slot and the nearly-broken one in the second slot. This will allow you to save money by preserving potentially expensive enchantments. However, it resets the Compact counter, making Compact IV the highest attainable level on a Pickonimbus 2000 as of the 0.19.1 update. It will also not preserve any reforges.
There is no warning before the Pickonimbus breaks, so you should watch out if you're trying to preserve enchants.