Potassium isotope dating
The boxes on the next few pages present a brief tutorial in rocks, minerals, and radioactivity.
Certain minerals, such as zircon and monazite, which form as common trace constituents in igneous rocks, have crystal structures which can accommodate varying amounts of the naturally occurring radioactive elements, uranium and thorium.
Both types of igneous rocks comprise a mixture of different minerals.
As igneous rocks cool, mineral crystals form following a specific sequence.
This was never fully successful as the size/intensity of an observed damage halo was also a function of the abundance of radionuclides present in the inclusion, and the crystalline structure of the host mineral. First is his contention that the granitic rocks from which samples reportedly came constitute the "primordial" crust of the Earth.
Within these rocks are biotite (an iron-bearing form of mica) and fluorite crystals which bear a relatively uncommon class of tiny, concentric discoloration "haloes" (figure 2).
Metamorphic rocks represent alterations of precursor sedimentary, igneous, or other metamorphic rocks.
From these observations early attempts were made to use the dimensions of haloes as an age dating technique.s the creation/evolution debate continues, there has been an increasing sophistication of certain Creationist arguments and publications.It can be an especially difficult challenge when the Creationist author has professional credentials and has published in mainstream scientific journals.The crystals develop an interlocking texture with some of the trace minerals becoming completely surrounded by later forming crystals.Volcanic rocks, because they are able to cool and crystalize rapidly, have a very fine-grained texture; the individual mineral grains are too small to see easily with the naked eye.