Not all secondary deposits are the same

I was reading some information from GIA about the MRM deposit which I found interesting. People seem to be quoting this "secondary deposits are higher quality" mantra. Well, it seems that is actually not true, and they seem to varying a lot in in yield and quality.

Take it for what you will. I'm not trying to downramp. I hold no stock and have no spare cash to do so at any price. Maybe this has been discussed before (I haven't been following MUS for long) so apologies if it has.

Hopefully some people find the below of value.

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PRODUCTION
As part of its bulk sampling operation, MRM has handled around 1.8 million tons of rock at Montepuez, recovering approximately 8 million carats of ruby and sapphire of various colors. The company hopes to double its capacity to 3.6 million tons of rock in 2015 and eventually increase that figure to 10 million tons of rock a year.

The actual recovery of ruby in the secondary deposits is more difficult to predict. The amount of ruby per ton can vary dramatically, and so can the quality of the rubies recovered. For example, the recovery rate in Mugloto pit 3 is relatively low: 0.60–1 gram per ton of ore processed. Yet the pit yields high-quality ruby, making it economically advantageous to sample, even with the low recovery rate. This pit also produces some large rough crystals of 6–8 grams. For comparison, Maninge Nice has a higher recovery rate of 20–35 grams per ton, but generally produces much lower-value material.

Overall, the recovery rate for the primary deposit is around 162 carats per ton, while the secondary deposits produce 31 carats per ton. The figure for the secondary deposits includes only processed gravels and not the amount of overburden topsoil moved.