Techniques for collecting representative sub-volumes from a large volume of geologic material. The particular sampling method employed depends on the nature of the material being sampled and the kind of information required. Common methods are: (a
) random sampling, a non-systematic or haphazard distribution of sampling locations; (b
) systematic sampling, a regularly spaced distribution of sampling locations; (c
) stratified sampling, a sequentially spaced, vertical distribution of sampling locations based on sampling each stratigraphic unit
in a succession; (d
) grab sampling, the collection of material using an externally controlled, mechanical grab (a method often used when sampling the sea floor or the surface of another planet); and (e
) chip sampling, the collection of borehole
drilling chips that are carried to the surface by lubricating mud and are representative of the material traversed by the borehole.