How is Argon Obtained???
Argon can be captured from the air by the distillation of liquid air. Argon is usually a by-product of the production of Nitrogen and Oxygen, since its boiling point is between the boiling points of these two elements.
It is also the decay product of the rare radioisotope potassium-40. This radioisotope has a very long half-life of 1.25 billion years, and Argon is formed from its disintegration. Since the Earth was formed, the gas has leaked into the atmosphere from the rocks containing potassium-40.
So, Argon is found in the air and in rocks containing potassium-40.