Page "Granite" Paragraph 47

Some granites contain around 10 to 20 parts per million of uranium.

By contrast, more mafic rocks such as tonalite, gabbro or diorite have 1 to 5 PPM uranium, and limestones and sedimentary rocks usually have equally low amounts.

Many large granite plutons are the sources for palaeochannel-hosted or roll front uranium ore deposits, where the uranium washes into the sediments from the granite uplands and associated, often highly radioactive, pegmatites.

Granite could be considered a potential natural radiological hazard as, for instance, villages located over granite may be susceptible to higher doses of radiation than other communities.

Cellars and basements sunk into soils over granite can become a trap for radon gas, which is formed by the decay of uranium.

Radon gas poses significant health concerns, and is the number two cause of lung cancer in the US behind smoking.