Final carats tally comp., page-93

Yeah, but they plan to do at least this much three times a year and much lower cost than any small cap gold company - the more you try and compare gold and rubies the less credible you get.

In terms of a single "mineral" from a single "asset" for a reasonable cost to produce and somewhat limited market (but ignoring sovereign risk) Galaxy is probably the closest peer worth examining if you want a yield comparison to SP - see where that takes you.