Who discovered potassium argon dating
Next, the mineral sample is heated to melting in a vacuum furnace, driving out all the gas.
By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined.
Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).
The rock samples are crushed, in clean equipment, to a size that preserves whole grains of the mineral to be dated, then sieved to help concentrate these grains of the target mineral.
The selected size fraction is cleaned in ultrasound and acid baths, then gently oven-dried.
Potassium occurs in two stable isotopes (Ar atoms trapped inside minerals.
Geologists have used this method to date rocks as much as 4 billion years old.It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40).
These each have 19 protons and 21 neutrons in their nucleus.Young rocks have low levels of Ar, so as much as several kilograms may be needed.Rock samples are recorded, marked, sealed and kept free of contamination and excessive heat on the way to the lab.If one of these protons is hit by a beta particle, it can be converted into a neutron.With 18 protons and 22 neutrons, the atom has become Argon-40 (Ar-40), an inert gas.These steps help remove as much atmospheric Ar from the sample as possible before making the measurement.