On rare occasions, it may be possible to investigate an anomaly by examining the rocks that occur as outcrop at surface. But in most cases the rock that generates the anomalous signature is buried underneath overburden or is found beneath a lake. Drilling must then be conducted to investigate the anomaly and recover samples.
A drill rig is positioned above the target and a hole is drilled. As the drill penetrates to depth, a continuous sample of the intersected rock is cored and retrieved for examination by geologists. Exploration drilling is expensive. Given that preliminary diamond analysis require only a limited amount of kimberlite; a typical discovery is generally assessed by one or two holes. If the drill core recovered is not kimberlite, drilling of the anomaly is generally discontinued.