Is it true that naturally occurring radioactive material from a specific type of rock is the same?
For example the gold-bearing rock in Australia and that from Tanzania.
What do you mean with "rock is the same"? When one of it is from Tanzania and the other is from Australia it is certainly not the same rock material.
The two rocks may be composed of similar mineral types, both bearing some gold and have some of the radioactive decay series start materials incorporated into mineral grains as explained below.
In natural materials such as rocks there are four natural radioactive decay family-series (1. Thorium-family starts with 232-Th, ends with stable 208-Pb, 2. Neptunium-family starts with 237-Np, end with stable quasi stable 209-Bi , 3. Uranium-radium-family starts with 238-U, ends with stable 206-Pb, 4. Actinium-family starts with 235-U, ends with stable 207-Pb). Depending on the age of the rock the isotopic abundance ratio between start and end nuclide of these series differs. A small ratio indicates a younger age than a large one. Apart from this there may be very different non-radioactive minerals in different amounts composing the rest of the radioactive rock material. You can even have a mixture of mineral materials from the radioactive decay series and when you do the sampling to analyse the material you should consider the heterogeneity of the rock from which you sample and do the observations (quantiative or qualitative measurements). The formation processes of these two gold-bearing rocks from two different continents should most probably be different as well.
No. NORM in a type of rock is not the same if the rock is from different locations. The concentrations of uranium, thorium, and potassium vary in rock in the same formation. Types of rock tend to have a higher concentration of say, thorium than uranium, but there is no way of predicting if every rock of that type will be have more thorium than uranium.
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