How do you determine the orgin of a rock sample? - Answers

The first step would be to determine what type of rock it is, based on the classifications of igneous, sedimentary, or metamorphic. All three have sets of characteristics common to them that indicate their method of formation. Beyond that, to find the actual place of origin geographically of a specific rock sample that may have been transported by erosional processes far from its place of origin, you would have to have some knowledge of formations--bodies of rock with specific characteristics that are found only in that formation. Factors to look at in the sample would be texture, type, fossils, and mineral composition.