Geologists distinguish these types of rock based on their chemical and mineralogical composition.
Figure 1 shows a typical discoloration halo around a radioactive mineral inclusion in the mineral pyroxene.
Mikhail Marov of the Vernadsky Institute of Geochemistry and Analytical Chemistry said scientists had determined the meteorite's age by observing the amount of radioactive isotopes and their decay byproducts, a technique called of a granodiorite at the Cuttaburra A prospect indicates that this mineralised system may be Middle Silurian in age and thus indicating that the host rocks are older than those hosting the Cobar-type deposits.
s the creation/evolution debate continues, there has been an increasing sophistication of certain Creationist arguments and publications.
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.
When these minerals occur as inclusions in certain other minerals, most notably the mica family, they are often seen to develop discoloration, or "pleochroic" haloes.