A compound is a substance that contains two or more elements close elementA pure substance that is made from only one type ... limestone, shale, and sandstone are all examples of sedimentary rocks.

For most organisms on Earth, rocks are objects, not food. But for one oddball microbe, desert limestone seems to have been on ...

Mysterious tunnels in desert rocks may be the work of unknown microbes, hinting at a hidden world inside marble and limestone ...

Mudstone, shale, and limestone are examples of sedimentary rock likely to contain fossils ... Throughout the earth's history, each of the three rock types has been continuously formed and recycled ...

Unusually small burrows, i.e., tiny tubes that run through the rock in a parallel arrangement from top to bottom, were discovered in marble and limestone of these desert regions. In the desert ...