Naturally occuring forms of precious metals, for example, native copper, native gold, and native silver.
Native metals are often very impure.
Compare with isotopic abundance . The average fraction of atoms of a given isotope of an element on Earth. A mixture of methane and other gases, found trapped over petroleum deposits under the earth. A valve which allows fine control over the rate of gas or liquid flowing through it. The valve contains a thin needle with a point that fits into a conical cup.