Granite

A coarse textured igneous rock, normally acid in nature and containing visible quartz, feldspar and coloured minerals (usually mica.) It is the result of the slow cooling of molten rock material at considerable depth beneath the earth’s crust. Granites tend to contain higher concentrations of radioactive materials with vein deposits of uranium exceeding 1000 parts per million. However, sedimentary rocks may well have been formed from rocks rich in uranium, or uranium bearing fluids may have migrated though them in the past. It follows therefore that rocks other than granites may contain enough uranium to give rise to a radon problem.

Uranium in Rocks

Average levels in parts per million (ppm)

Granites 4.0ppm

Shales 3.7ppm

Carbonates 2.2ppm

Sandstones & Basalts 0.5ppm

Vein Deposits of Uranium > 1000ppm

The rocks most commonly enriched in uranium include:

Granites

Carbonaceous Shales

Phosphatic Rocks