Fission track dating attempts to calculate the age of a mineral or glass by using either of two methods being spontaneous or induced, which engages (‘two different isotopes of uranium, U-238 and U-235 respectively’) (Walker, 2005: 115-117). Most uranium decays into a stable lead but occasionally the atom splits in two at a high speed damaging the surrounding structure. By observing a polished slither of the material under an electro-microscope you can see the tracks left by this (spontaneous fission), then by counting the fission tracks left behind, it is possible to calculate an age for the object in question (Bahn 2008:152-154; Greene 2002:170-171; Walker, 2005: 115-117).
Irving Friedman and Robert Smith developed obsidian hydration (rind) dating in 1960. If an obsidian (recently deposited volcanic) object, is trapped for a long period in an area where water is present, water vapour will slowly diffuse into a freshly chipped surface. The cumulative hydration or absorption of water will form a hydration layer, measurable in microns on the exposed surfaces. These layers are then detected, when a small section of the object is removed, ground, and placed on a microscope slide, where the hydrogen band is measured (Bahn 2008:159-160; Greene 2002:175-176; Trembour and Friedman 1984: 141-152).
Since the hydration rate, with respect to a specific obsidian composition and water temperature is constant, if the obsidian composition is known and the historical temperature of the area was constant year after year, or if regional correction factors are known, accurate dates can be produced. In the right circumstances, this technique can be used to date objects as recent as present or as ancient as 120,000 BP (Bahn 2008:159-160; Greene 2002:175-176; Trembour and Friedman 1984: 141-152).
Probably the most well known electromagnetic dating technique is that of archaeomagnetism, introduced into the field of archaeology by Robert Dubois in the 1960s. Archaeomagnetism uses the scientific fact that the Earth's magnetic field varies through time, and shifts in the horizontal plane (declination angle) as well as the vertical plane (dip angle) (Bahn 2008:161-162; Greene 2002:176-178; Verosub and Roberts 1995: 2175–2192).
This method requires the sample of rock or clay tested, to have undergone (superheating) hotter the prehistoric firing methods. The iron particles trapped within minerals, when superheated above its curie point, align with magnetic north thereby, the minerals orientation is fixed to that current magnetic baring. In some areas,
archaeomagnetic alignments have been calibrated to 4,000 BP (Bahn 2008:161-162; Greene 2002:176-178; Verosub and Roberts 1995: 2175–2192).
Potassium – Argon Dating:
Potassium – argon dating, and Argon-argon dating, were both extensions of Jeffery and Reynolds iodine-xenon studies of meteorites at University of California, Berkeley, in 1961. Both these methods are more precise in their execution, and are both used in archaeology and geochronology. Potassium-argon dating measures the product of the radioactive decay of isotope potassium-40, which decays into calcium-40 and argon-40 (Bahn 2008: 149-150; Pitman 2008; Greene 2002: 168-69).