Uranium is soluble in acid waters and tends to be removed in solution, but radium is much less soluble and its compounds tend to remain behind in the leached outcrop. Therefore, the outcrop may be radioactive due to the presence of the gamma-emitting elements RaC and RaD, even though much of the uranium has been lost in solution. In this case a radiometric assay may indicate a high counter reading, but the uranium content may be low. Uranium minerals deposited less than a million years ago may be in inequilibrium because daughter products have not accumulated in their equilibrium amounts. Hence, counter readings may indicate less uranium than is actually present.