Bryson Burke Diamond Corporation
© 2001 - 2004

 

 

 

 

 

 

 

 

 

Lamproites are much less susceptible to prospecting by this method, as they lack the classical kimberlitic indicator minerals. Leighton and McCallum (1979), suggested that the maximum transportation distances before complete disaggregation for the classical indicator minerals was 1.5 miles (ilmenite), 1 mile (pyrope garnet), and 0.25 mile (chromian diopside). During mapping of the Iron Mountain district in 1998, the WSGS recovered samples of consolidated kimberlite cobbles 0.75 mile downstream from the source outcrop. This would suggest that the maximum transport distance for the three indicator minerals would be more on the order of 2 to 2.5 miles for ilmenite, nearly 2 miles for pyrope garnet, and 1 mile for chromium diopside. The presence of these minerals in stream sediment samples suggests a nearby source kimberlite intrusive(s).

Other indicator minerals include chromite, olivine, chromian enstatite, and diamond. Maximum transportation distances for chromite is similar to ilmenite, olivine similar to garnet, and chromium enstatite similar to chromium diopside. Diamond is not considered a good indicator unless found in a closed drainage basin. Diamond transportation distances in Africa are as much as 500 to 1000 miles.

Stream sediment sampling is labor intensive. It is accomplished by panning with traditional gold pans and sieves, then transporting the panned concentrates to a lab for microscopic examination to look for kimberlitic indicator minerals. Typically, it takes a field crew of two to recover a maximum of 3 to 4 samples per day. Ideally, the spacing of samples for optimum coverage is only about one mile on accessible drainages.

The sample concentrates are further processed in the laboratory, before microscopic examination, which is also labor intensive.