Ann: Lab Results Confirm Kimberlite Target Areas, page-156

According to company papers, Angolan kimberlites are well preserved with limited erosion as they were preserved by the Calonda Fm and Kalahari Fm shortly after emplacement. This gives them the "champagne glass" profile. On the other hand, South African kimberlites are usually more eroded and have a carrot shape.
I cannot say for sure how much RVK sits above PK. That's why the upcoming geophysical survey and drilling are so important. As L259 is a low lying kimberlite that was possibly beneath a small lake, I suspect there is a thick layer of sediment overburden and RVK on top. The company has been trenching the site for a while now and have still not mentioned finding the edge of this kimbo. Management are being very systematic with their approach which is good to see. The survey currently being conducted should map out the overall structure of the kimbo. Then delineation drilling will begin which should give you your answer with regards to the thickness and boundaries of the RVK and PK interfaces.
The last phase will be drilling for PK samples and bulk sampling the PK to check for diamond content.