Quick search by citation:

30 U.S. Code § 28–2 - Definitions

As used in section 28–1 of this title,
(a)
The term “geological surveys” means surveys on the ground for mineral deposits by the proper application of the principles and techniques of the science of geology as they relate to the search for and discovery of mineral deposits;
(b)
The term “geochemical surveys” means surveys on the ground for mineral deposits by the proper application of the principles and techniques of the science of chemistry as they relate to the search for and discovery of mineral deposits;
(c)
The term “geophysical surveys” means surveys on the ground for mineral deposits through the employment of generally recognized equipment and methods for measuring physical differences between rock types or discontinuities in geological formations;
(d)
The term “qualified expert” means an individual qualified by education or experience to conduct geological, geochemical or geophysical surveys, as the case may be.