Portland stone is a type of rock that we use to build buildings and other cool things. Imagine you're playing with some silly putty and you squish it between your hands. Do you notice how it's smooth and flat? Portland stone is kind of like that, but it's much stronger and doesn't stretch like putty.
People have been using Portland stone for thousands and thousands of years because it's so strong and lasts a long time. You can find it in many famous buildings all over the world, like Buckingham Palace in England and the United Nations Headquarters in New York City.
Portland stone is made when tiny sea creatures and other things that live in the ocean die and their bodies pile on top of each other. Over time, the layers of sand and shells and other things gets squished together, and that's how we get Portland stone!
It has a very light color, like a very bright white or creamy color, and when it's cut and shaped, it looks very beautiful. Because it is strong, it can be used to build big, tall buildings that can stay standing for a very long time.