It's not that hard to make a guess.
From ABZ forum: Stockwatch:
Author: WillP -- Date:1999-05-18 16:39:03
Subject: Yet Another Diavik Analysis
Greetings:
The question has arisen elsewhere as to what percentage of gems greater than 1 carat exist in the Diavik pipes.
Here's a rough guess:
Caustic fusion results returned 5 diamonds larger than one carat in 4.5 tonnes of rock from A154-S and A418.
Personally, I estimate one such stone for every tonne of kimberlite. Also, it appears that 75% of the value of Diavik pipes are contained in stones larger than one carat.
I've seen figures bandied about that Ekati diamonds of fine quality run about 30% of total production...and at Diavik, it's about 15%. Hearsay, of course...but my calculations tend to support the suggestion.
At that rate, every 7 tonnes should contain one such diamond.
Using the 75% of value bit...the average value of such a stone would be around $1,400 US.
I think that between 25 and 30% of those stones will exceed 2.0 carats, and possibly 5% will exceed 4.0 carats. Those stones, of course, would carry much more value than the smaller ones.
Put another way...Diavik likely contains a 1 carat fine gem every 7 tonnes or less, and a 2 carat gem every 25 tonnes. A 4 carat gem I expect every 200 tonnes.
The 1-2 carat stones would have value of $600 per carat, the 2-4 carat stones would have value of $1100 per carat, and the 4+ carat stones a value of 1500 per carat, on average.
Working backward...a 200 tonne sample (that's a mathematical accident, I assure you) would have one 4.5 carat gem worth about $6600, 8 stones between 2-4 carats with an average value of $2650, and an additional 21 gems between 1-2 carats, worth an average of $750.
In total, that totals $43,500 US per 200 tonnes...or $220 per tonne. It also totals just under 50 carats. So...the A154 south and A418 pipes have an effective plus one carat fine gem grade of 0.25 carats per tonne...which probably accounts for 75% of the value. (My rough calculations above are 78%...but it proves the point nicely.)
Look at it another way...Gren Thomas' statement that the A154 South bulk sample diamonds would fit in a coffee can and 70% of the value would fit in a shot glass. That's a normal value distribution.
Very roughly, from memory, $60 per carat...and 12,000 carats (2.4 kilos) the total value was $720,000 US. A 1.5 ounce shotglass would hold about 5 ounces of diamonds, or 750 carats. So, 6% of the diamonds by weight accounted for 70% of the value. The pipes would have an effective grade of 0.25 carats per tonne, for diamonds of this calibre. The average value of these diamonds would be just under $700 US per carat.
The reasons for Diavik's "low" per carat value are:
#1...Abundance of smaller stones, and relative infrequency of stones larger than 10 carats.
#2...Relatively low percentage of gem quality stones.
However...value is contained in only the finest and largest stones. In order to have respectable value...you have to have such stones.
It's impossible to have a value of $300 per tonne, without having an abundance of the clearest, larger, flawless stones.
Diamond prices drop off exponentially, after all.
Diavik diamonds are going to be hard to beat. :-)
Regards,
WillP |
