RE: Different subject : AshtonRead it again, and pay attention to the width of kimberlite sampled, then think about Shore's widths (whose widths are measured in tens to hundreds of metres, over an area measured in hundreds of metres to kms):
"The dyke exposed at Trench 184 has a true width of approximately 0.4 metres and is interpreted to dip to the east-northeast at approximately 30 degrees. The 6.2 tonne sample of kimberlitic material from this trench returned an estimated diamond content of 36 cpht, including a 0.49 carat clear tetrahexahedroidal diamond.
Trench 221
The area exposed at Trench 221 consists of a zone of kimberlitic dykes with an estimated cumulative true width of 1.7 m including the entrained country rock. The cumulative width of kimberlitic material is approximately 1.1 m, with the thickest individual dyke measuring 0.7 m. At this location, the dyke system is interpreted to dip to the east-northeast at approximately 20 degrees. "