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These discoveries had a long-lasting influence on crystallography because they led to the development of the X-ray powder diffractometer, which is now widely used to identify minerals and to ascertain their crystal structure.Advanced analytic chemical equipment has revolutionized the understanding of the composition of rocks and minerals.

Such techniques have had an enormous impact on scientific knowledge of Earth history because precise dates can now be obtained on rocks in all orogenic (mountain) belts ranging in age from the early Archean (about 4 billion years old) to the early Neogene (roughly 20 million years old).Versions of the modern mass spectrometer were invented in the early 1920s and 1930s, and during World War II the device was improved substantially to help in the development of the atomic bomb. By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay (each radioisotope has its own decay constant), the isotopic age of the sample can be calculated.For dating minerals and rocks, investigators commonly use the following couplets of parent and daughter isotopes: thorium-232–lead-208, uranium-235–lead-207, samarium-147–neodymium-143, rubidium-87–strontium-87, potassium-40–argon-40, and argon-40–argon-39.For example, the XRF (X-Ray Fluorescence) spectrometer can quantify the major and trace element abundances of many chemical elements in a rock sample down to parts-per-million concentrations.This geochemical method has been used to differentiate successive stages of igneous rocks in the plate-tectonic cycle.

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