Theorized quark stars may be made of quarks. But if you “compress” the Dinosaur eating Reindeer Christmas shirt and by the same token and matter beyond that, what kind of matter is it? No kind. Matter is matter because it occupies space and time. A black hole is a black hole because it does not. Or at least not in the way that particles do. That is why it is called a “singularity”. It is a point. It does not have a width or a depth. It does not have a 3 dimensional volume. There is no “space” inside a black hole. There is no “inside” in a black hole. It is a singularity. The material that made it has been squeezed OUT of our world. It still exists BUT it does not “exist” in the way we understand matter or particles to exist in our space. We don’t have to guess what it is made of. It is made of mass. Only mass.