From the Deadly Art of Stock Manipulation,

RULE NUMBER ONE: ALL SHARP PRICE MOVEMENTS -- WHETHER UP OR DOWN -- ARE THE RESULT OF ONE OR MORE (USUALLY A GROUP OF) PROFESSIONALS MANIPULATING THE SHARE PRICE."

This should explain why a mining company finds something good and "nothing happens" or the stock goes down. At the same
time, for NO apparent reason, a stock suddenly takes off for the sky! On little volume! Someone is manipulating that stock, often with an unfounded rumor.

In order to make these market manipulations work, the professionals assume: (a) The Public is STUPID and (b) The Public
will mainly buy at the HIGH and (c) The Public will sell at the LOW.
Therefore, as long as the market manipulator can run crowd control, he can be successful.