Rocks and minerals hold precious clues about how Earth formed and evolved over billions of years — but what is the difference between the two?
Each type of mineral has a unique crystal structure, which results from its chemical composition and a set of physical properties, such as hardness, color or magnetism, according to the United States Geological Survey . For instance, halite — the natural form of sodium chloride , from which table salt is made — is a soft mineral that forms clear, cube-shaped crystal fragments.
A good example of a mineral is quartz, which is found across the world and in different rocks, such as granite and quartzite, Anderson said. Quartz is made of the chemical elements silicon and oxygen and has the chemical formula . The mineral is colorless in its pure form, but impurities can either make quartz crystals appear opaque or stain them pink, purple, yellow or brown.
While some minerals like halite have relatively simple crystal structures, others can contain 10 or more elements, such as khomyakovite and georgbarsanovite. Igneous rocks — which form as magma solidifies either deep within Earth or at the surface after a volcanic eruption, for example — contain a limited number of minerals that crystallize, Richard Bevins, an honorary professor of Earth sciences at Aberystwyth University in the U.K., told Live Science in an email."These are termed the common rock-forming minerals and include feldspar, olivine, pyroxene, mica, quartz and amphibole.