Rubidium 87 radioactive dating
Note that the halo has the highest intensity of discoloration near the source, gradually fading with distance in the host mineral to a "fuzzy" edge.Radiation damage haloes around mineral inclusions are well known from the geological literature.These haloes were considered to be the result of damage to the crystal structure of the host minerals caused by high energy alpha particles.In numerous papers published in scientific journals in the 1970s and 1980s, Gentry built the case that the different alpha decay energies of various naturally occurring radioactive isotopes resulted in distinctly different halo diameters.
Geologists distinguish these types of rock based on their chemical and mineralogical composition.
Plutonic rocks on the other hand cool very slowly, on the order of a million years or more for some deeply buried and insulated magmas.
The mineral grains in these rocks can grow very large and are readily distinguished in hand samples.
When burial pressures and temperatures get too great, the rocks melt completely, becoming new igneous rocks.
To fully understand Gentry's hypothesis a basic background in geology, mineralogy, and radiation physics is helpful.
Metamorphic rocks represent alterations of precursor sedimentary, igneous, or other metamorphic rocks.