Quartzite, a metamorphic rock derived from sandstone. In some quartzite the sand grains are recemented with silica. In others the metamorphism (change) of the sandstone results from great pressure. Quartzite is extremely hard and highly resistant to chemicals. It has a glassy luster and may be white, gray, pink, or brown. Quartzite is used in making glass and to pave roads.
A black hole occurs when a massive star dies -- its enormous mass implodes and becomes so heavy that it bends space. So how do astronomers detect something that they can't see?
While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter.