Naxian marble is a type of rock that is found on the Greek island of Naxos. It is special because it is very strong and can be used to make things like statues or buildings that last a very long time.
Think of it like building blocks that are really tough and sturdy. When people want to make something that will last a really long time, they might choose to use Naxian marble because it is so durable.
So, if you were building a sandcastle at the beach, you might use regular sand that is easy to mold and shape, but if you were building a big castle that you wanted to last forever, you might use Naxian marble "blocks" because they are stronger and more durable.