On the microscope here, the stereo microscope
under regular light, I have two diamonds.
I have a rough diamond here from Letseng,
a mine in southern Africa at the southern margin of the Kaapvaal
Craton.
And this is a rough diamond.
It's pretty resorbed.
And you can see one black grain in the middle which
is a sulfide inclusion decorated by a rosette fracture
system which makes it look much bigger than it actually is.
The actual sulfide inclusion is at the center of this dark area
here.
And in comparison, next to it I have a plate,
a diamond plate with four inclusions.
And this is from the Helam mine which
is in the center of the Kaapvaal Craton, a mine that
hasn't been mined extensively.
In this particular rough diamond,
you can see the exterior rough surface here.
We've cut from that rough diamond, a plate that's
probably about a millimeter thick, polished
it on both sides.
And in that plate are four inclusions.
You can see them here.
And again, each one of these inclusions
is decorated by a fracture system.
And the sulfide inclusion is actually
at the center of the fracture systems.
In fact, on this one here, you can see this very shiny area.
That's the inclusion.
And there's the fracture system.
These represent diamonds that have
been taken from active former mines or prospects or currently
active mines.
And the purpose here is to actually take these inclusions
out and date them using the rhenium-osmium system,
inclusion by inclusion.
And I'm going to show you how that process goes.
So what I have my hand here is a small collection
of diamonds, rough diamonds from the Letseng mine.
And this represents one trip to the Letseng mine
where a particular geologist, Steve Richardson,
went and picked from a collection, or a parcel
of diamonds, from the production of a couple weeks or a couple
months.
I'm not exactly sure how much production is represented.
He picked through a couple thousand diamonds, maybe more
and picked out the 10 or 20 that had sulfide inclusions
that we can analyze.
Inclusions are pretty rare.
They make up less than, sometimes less
than a percent of production.
And often don't make it into the gem trades.
So that's what the geologists are interested in.
But it's very seldom what the gemologist sees
unless it's a very tiny inclusion.
They're not going to be looking for the big inclusions.
So the next step is to take a good close look
at the samples on the microscope.
And the purpose here of looking at them under a microscope
is to see which direction I want to make the cut.
What we want to do is, we'll want
to come up with a picture of the particular external morphology.
And I'll put a couple dotted lines on there that
will show us the pattern of the laser
cut we want to make so that we can stay
outside of the fracture system.
We don't want the laser energy or the heat
to actually intersect this fracture system.
Or we might compromise the inclusion
and lose some material.
We want to actually remove the inclusion eventually
by breaking the plate.
And so you can see, on this particular plate
that we've made the cut on, none of those inclusions
in the fracture systems actually extend
to the polished surface of the plate.
The reason that we don't want that to happen
is because when you polish the diamond, it can get warm.
And you're going to polish it on a wheel that's got iron on it.
And you could introduce oxidation
to that fracture system.
And you can compromise the inclusion with the heat.
So we want to isolate it within the diamond.
We're essence in using-- In a sense,
we're using the diamond as a holder for the inclusion
until we're ready to break it out.
And that's actually a pretty handy aspect of this research
is the diamond is one of the better unbreakable
type of containers to work with a small inclusion.
So it's actually a little nice feature
about having your diamonds around the inclusion you
want to get at.
So these diamonds are two to three millimeters.
I think they're probably less than a quarter
of a carat, maybe half a carat, something like that.
They're not really big diamonds.
They would not be very expensive on the open market.
To us, they're priceless.
But on the open market, we can probably buy enough diamonds
to do a study with for a couple thousand dollars.