Excellent program last night on “Peace of Africa” dredging up 400
tons of gravel/hour to find 57 carats of diamonds.
Could you please explain the “magnetism” of diamonds? We were told
that they are naturally magnetic and so iron filings are attached to
them in the milling process which gives them extra weight. Then a
"flotation" process like gold panning is used to separate the heavy
iron-diamond stones from the rest.
Never saw a diamond attract iron. Magnetism is used to separate
magnetic junk from diamond gravel before further processing. Also,
magnetic powders are used to make dense liquid for separation of
diamonds. Diamond is relatively heavy, so most stuff floats in the
dense medium and the diamonds sink. Look up “dense media separation.”
Al Balmer
Sun City, AZ
Some synthetic diamonds are magnetic. But diamonds are not.
Never saw a diamond attract iron. Magnetism is used to separate magnetic junk from diamond gravel before further processing.
That surprised me but it is exactly what they showed on Discovery,
adding that these diamonds have natural magnetism.
Diamonds have a very rough surface at the microscopic level and are
dense compared to most alluvial materials [4.1 compared to 2.75 for
quartz sand] They are usually dredged and separated by passing over a
greased wrinkly sloping table or tube where their weight and
roughness make them stick in the undulations of the rubber. You can
also do centrifugal separation where the high SG also makes them
sink and the rest of the gravel float. I used to do work analysing
all the heavy minerals associated with diamonds for several mining
companies as diamondiferous rocks have a unique chemistry [so does
platinum bearing rock]. one of the ways of separating some of these
important tracer minerals is by magnetic separation- this is where
you pass the material down a slope in a powerful magnetic field and
these minerals will then take a different route to the dross. I
suspect that the TV programme didnt explain these differences very
well and thus gave the impression the diamonds were magnetic.
Nick
Sounds like the usual miss-given out to keep Joe Public
from starting up their own [insert industry of choice here] business.
De-Beers is very good at this practice…
As already mentioned diamonds aren’t magnetic, but magnets are used
in the their mining.
Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com
As already mentioned diamonds aren't magnetic, but magnets are used in the their mining.
There is, though, if I recall correctly (and it’s been a while, so
this might be out of date), one slight exception to the above. Some
synthetic diamonds have inclusions in them, if I recall it right,
that allows those diamonds to be very slightly attracted to a
magnet, with that being an indication of the synthetic origin of
those stones… Is that a correct memory?
Peter Rowe
one of the ways of separating some of these important tracer minerals is by magnetic separation- this is where you pass the material down a slope in a powerful magnetic field and these minerals will then take a different route to the dross. I suspect that the TV programme didnt explain these differences very well and thus gave the impression the diamonds were magnetic.
There is another possibility. The best candidates for the Pegasus
process are brown and yellowish-brown diamonds. Mineral responsible
for brown color in diamonds is magnetite. It is possible that such
diamonds can attract iron filings. What they were doing was
separating diamonds suitable for Pegasus process, but they did not
bother to explain it to movie producers.
Leonid Surpin
Some synthetic diamonds are magnetic. But diamonds are not.
Chris is right - prior to man-made diamonds, only metals were
magnetic.
Apparently, synthetic magnetic diamonds were created in the lab
starting around 2005 to provide nano-science a non-metallic substance
to work with. There is not a lot of current on these
scientific oddities, other than these diamonds are very small.
Diamonds were picked not because of their intrinsic value but because
they are made of carbon.
Some synthetic diamonds have inclusions in them, if I recall it right, that allows those diamonds to be very slightly attracted to a magnet, with that being an indication of the synthetic origin of those stones... Is that a correct memory?
Yes.
Wayne Emery
www.thelittlecameras.com
There is another possibility. The best candidates for the Pegasus process are brown and yellowish-brown diamonds. Mineral responsible for brown color in diamonds is magnetite. It is possible that such diamonds can attract iron filings. What they were doing was separating diamonds suitable for Pegasus process, but they did not bother to explain it to movie producers.
I think it is the latter because they did not “imply” the diamonds
were magnetic. They stated it explicitly and yes they said iron
filings were attached to the diamonds to give them greater weight in
the separation.
There is, though, if I recall correctly (and it's been a while, so this might be out of date), one slight exception to the above. Some synthetic diamonds have inclusions in them, if I recall it right, that allows those diamonds to be very slightly attracted to a magnet, with that being an indication of the synthetic origin of those stones... Is that a correct memory?
Yes.
From this article, it appears that natural diamonds can have some
magnetism, caused by surface inclusions, but it disappears with an
acid wash. Also, there are thermal treatments which eliminate the
magnetism in synthetics, so it’s not a useful test.
Al Balmer
Sun City, AZ
In the early processes used to create synthetic diamonds iron as
well as manganese, cobalt, nickel, palladium, and platinum were used
as solvents (pg 181, “Gems Made By Man” by Kurt Nassau). Those
synthetic diamonds created in a solvent with iron would sometimes
have iron inclusions in them thereby making them susceptible to
magnetic influence (Refer to GIA’s Gem Reference materials). Such
magnetism isn’t always present, but if it is it an indicator of a
synthetic diamond.
For those wondering how iron could be a solvent, I suggest you refer
to Mr. Nassau’s book, or perhaps one of our fellows has some
experience in hi-temp/hi-pressure chemistry.
Mike DeBurgh, GJG
Henderson, NV