| − | The [[mineral]] constituents of a [[rock]] that occur in such small amounts that they are disregarded in the definition and [[chemistry]]. | + | The [[mineral]] constituents of a [[rock]] that occur in such small amounts that they are disregarded in the definition and [[chemistry]].<ref>*Pellant, Chris. ''The Complete Book of Rocks and Minerals'', Dorling Kindersley Inc.: New York (1995) page 250</ref> |