Lilydale topping is crushed lime stone, spread loose by shovel and then rolled in and compacted and after wetting it settles as hard as concrete.
But it can easily be dug up with a pick (eg. to get at or install a drain) and relaid again. I have used it extensively in my garden for paths and it is easily maintained and very durable.
BTW I used crushed rock as a base at that is cheaper.
Peter.