Primarily, the company used a lower cut-off value – the point at...

Primarily, the company used a lower cut-off value – the point at which the amount of rare earths in the rock (known as the grade) is so low that it’s no longer economical to mine it as you don’t get enough valuable material.Vital said the new cut-off value was derived from a more sophisticated calculation than the old one, taking into account commodity prices and other factors to suggest Vital could profitably mine more material at Tardiff than it previously thought.

Who can validate that their new approach is legitimate? How can we be confident that this isn't some figure inflation to make the project more attractive?