Pretty well known fact and plenty of sources to back it up,...

Pretty well known fact and plenty of sources to back it up, here's one.

"current surface grades at Marange are 3.75 carats per tonne. A month later, Jinan Investments Ltd’s chief mining operations officer publically commented that deeper conglomerate rock grades drop to 0.4-0.5 carats per tonne, adding that they “are too expensive to extract.” Mining deeper conglomerate rock requires more advanced equipment, and some of the Marange companies are reluctant to put forth the capital expenditure necessary to procure the needed equipment."

http://www.*****.com/ind/Zimnisky/2...Largest-Diamond-Producer-For-Much-Longer.html

Still MUS may not be that bad of a gamble, more upside than LOM for sure.