Willp has decided to shed some light on indicator minerals, and help you with your project. You think he's listening to us (gggggggggg)
Majescor hopes garnets lead to diamonds
Majescor Resources Inc MAJ
Shares issued 8,703,691 Jan 21 close $1.62
Tue 22 Jan 2002 Street Wire
by Will Purcell
If diamond indicators and geochemistry means anything, Majescor Resources
and its partner, BHP Billiton, should have a busy time of it this year in
Northern Quebec, drilling for diamondiferous kimberlites on their Otish
Mountains project. Unlike Ashton Mining of Canada, Majescor's main rival in
the region, the partners do not yet have any diamond counts to tout. As a
result, Majescor shareholders have been left to ponder the results of their
company's preliminary work, including the analysis of the diamond indicator
minerals found till samples that were collected a few months ago.
The Majescor samples apparently did contain an encouraging array of
indicators that suggest that kimberlites found in the area could be
diamondiferous. One clearly promising sign was that about 30 per cent of
the pyrope garnets found were classified as G10 garnets. As well, an
analysis of the chromite grains led to a similarly promising conclusion.
Those signs pointed to there being a good chance that diamondiferous
kimberlites are present in the area, and the presence of ilmenites with a
high chromium and magnesium content offered promise that the diamonds might
be well preserved.
Touting a promising array of diamond indicator minerals in the absence of
diamonds themselves is certainly nothing new, although some explorers have
placed more faith in the technique than have others. Favourable
geochemistry has often translated into promising discoveries, but
frequently it has not -- at least not yet.
The concentration of G10 garnets is one of the most common techniques used,
although most explorers avoid specifics when touting their hauls of G10, or
subcalcic garnets. South-Africa-based John Gurney was instrumental in
developing the technique in the early 1980s. The calcium and chromium
content of the garnets is plotted on a graph, and those with a low calcium
and high chromium content sufficient to fall below a certain line on the
graph are classified as G10 garnets, minerals that originated within the
diamond stability field in the upper mantle.
Grains of chromite that are found in the till samples are also assessed to
determine if they may have originated from within the diamond stability
field. Promising grains are those with a chromium oxide content greater
than about 60 per cent, as well as a magnesium oxide content of at least 12
per cent. Kimberlitic ilmenites can be identified by their
characteristically higher magnesium content, with more a magnesium oxide
content greater than 4 per cent.
Although most explorers tout their geochemistry at one time or another,
comparatively few have offered specifics. That is hardly unusual however,
especially if the numbers are best forgotten; nevertheless, the actual
numbers frequently do leak out.
About one-quarter of the garnets contained in the A-154 South kimberlite,
discovered in 1994 by Aber Diamond Corporation, were apparently classified
as G10 garnets. Chromite grains contained good news as well, as about 28
per cent of them are believed to have contained favourable concentrations
of chromium and magnesium. That the pipe sampled the diamond stability
field is certainly without question. The first 700-kilogram batch of
kimberlite contained more than 100 diamonds longer than one millimetre, and
eight of them weighed at least 0.20 carat, including the 1.75-carat Aber
diamond. Subsequent work determined that the pipe had a commercial diamond
grade in excess of five carats per tonne, and the kimberlite is the
flagship of the four-pipe Diavik project.
Detailed information is not available for most of the other economic pipes
in the Lac de Gras area, but there is little doubt that they had favourable
concentrations of indicator minerals. Canadian diamond pioneer, Chuck
Fipke, has long been a believer in geochemistry, and the initial
discoveries were made in the Lac de Gras area after Mr. Fipke tracked
trains of indicator minerals across much of the Northwest Territories. As a
result, it is no great surprise that most of the promising Ekati and Diavik
kimberlites reportedly have G10 concentrations ranging between 10 per cent
and 25 per cent.
Chris Jennings is another big fan of geochemistry. The SouthernEra chairman
certainly has had success in identifying properties prospective for
diamonds, and his company has been a successful explorer for the gems
through the years. Nevertheless, promising geochemistry does not
necessarily lead to a promising diamond discovery.
One of those apparent failures occurred on the company's Munn Lake play, on
the Back Lake property, located about 100 kilometres to the southeast of
Lac de Gras. In the late 1990s, SouthernEra discovered the Yuryi kimberlite
float occurrence on the western shore of Munn Lake. About 40 per cent of
the garnets contained in that material were classified as G10s, and the
rock was also clearly diamondiferous. A 581-kilogram sample yielded 226
stones, including 62 macrodiamonds. There were some larger diamonds in the
mix, including a 0.12-carat stone, along with five others that weighed at
least 0.01 carat.
The diamonds were a pleasant surprise for investors, but it seemed that the
garnets were the best news for SouthernEra. The company drilled several
holes into a kimberlite sill in Munn Lake during 1999, but the diamond
content was modest. About 42 kilograms of kimberlite contained just 14
stones, and just two of those were macros. Although the kimberlite had
sampled the diamond stability field, the actual diamond content was not
much to write hole about, as things turned out.
SouthernEra and its junior partners also chased a kimberlite source for the
Margaret Lake kimberlite indicator mineral train, which was found on the
western shore of Margaret Lake. About 20 per cent of the garnets in the
two-kilometre-wide train were classified as G10s, which fuelled optimism
for some time. No kimberlite source for the train has been found however.
The company also acquired an interest in the Yamba Lake project, after
other explorers had failed, apparently on the basis of promising
geochemistry. A number of kimberlite had been discovered on the property in
the early 1990s, but none amounted to anything. SouthernEra believed that
it could succeed where others had failed, primarily because there were
unexplained indicator mineral trains with higher concentrations of
indicator minerals. None of those trains could be tied to the existing
kimberlites, which did not have the same high levels of indicator minerals.
For instance, less than 4 per cent of the garnets contained in the
low-grade Torrie pipe were G10s. Although SouthernEra has other interests
these days, the company still has not called it quits at Yamba.
One area where the company did call it quits is Brazil. SouthernEra struck
a deal with Canabrava Diamond that would allow it to earn an interest in a
large Brazilian property, but things did not work out. SouthernEra's high
hopes were based in part upon geochemistry. In 2000, the company said that
the property produced some of the best subcalcic garnets discovered in
Brazil. Unfortunately, that did not lead to the discovery of a diamond
deposit, and SouthernEra walked away from Brazil last year.
Twin Mining is another Canadian explorer to take advantage of toutable
garnets and chromites. The company's Baffin Island play has produced some
of the highest numbers obtained in Canada, and the Jackson Inlet
kimberlites do seem to be diamondiferous, with some larger stones in the
mix. Nearly 30 per cent of the garnets found in the Freightrain kimberlite
were classified as G10s, and nearly half of the chromites were considered
to be favourable as well. Samples of individual outcrops produced some
stellar values, with a G10 content ranging up to about 75 per cent. One
particular location, dubbed No. 2, has produced two diamonds weighing more
than 0.75 carat each, and that location has a G10 content of about 47 per
cent. Twin Mining is now processing a mini-bulk sample weighing a few
hundred tonnes, with results expected early this year.
Encouraging numbers of G10 garnets do not always lead to promising diamond
grades. Mano River Resources touted a promising array of G10 garnets in one
of its Liberian kimberlites, but that did not translate into an economic
diamond grade. About 29 per cent of the garnets in the hypabyssal phase of
the K-003 kimberlite pipe were G10s, and 54 per cent of the garnets in the
diatreme facies were subcalcic garnets. A 103.5-kilogram sample of
hypabyssal kimberlite contained no diamonds however, and the diatreme rock
did not fare much better. About 172 kilograms of material contained just 16
diamonds, including two macros. One of the stones was large enough to
remain on a one-millimetre screen, but the diamond content was too low to
offer much excitement to the market. Little has been heard of K-003, or the
rest of the Liberian play, of late.
Conversely, not all promising kimberlites display a high proportion of G10
garnets. De Beers continues to work at its Victor kimberlite project in the
Attawapiskat region of Northwestern Ontario, despite the almost total
absence of G10 garnets. Although the value contained in the lower-grade
pipe was recently deemed not sufficient to warrant a feasibility study, De
Beers continues to plug away at the project.
The absence of G10 in a diamondiferous kimberlite is not unique to Victor.
The prolific Orapa kimberlite in Botswana is perhaps the best example of an
economic kimberlite that did not display significant levels of G10 garnets.
Orapa has been in production for more than 30 years, with a grade of about
0.75 carat per tonne, and the mine produced over 12 million carats in 2000.
Geochemistry told a curious story at Snap Lake as well. Winspear initially
said that about 18 per cent of its garnets plotted within the G10 field,
although some company officials later stated that only a small proportion
of the pyrope garnets had classic G10 compositions. One unusual aspect of
the Snap Lake kimberlite was the high chromium content of the garnets.
Although G10 garnets rarely have a chromium content in excess of 12 per
cent, the Snap Lake garnets had a chromium content as high as 17 per cent.
The Snap Lake kimberlite dike will likely become Canada's third diamond
mine, with a grade of about two carats per tonne.
Kimberlites with a low diamond content often have a modest array of G10
garnets. For instance, many of the marginally diamondiferous kimberlites
that were discovered along the Timiskaming rift had very low concentrations
of subcalcic garnets, including the C-14, or Clifford, pipe that produced a
number of larger macrodiamonds, but had a microscopic diamond grade. Recent
work suggests that the region further to the southeast may have more
promise, based on the G10 content. Some of the mineral trains around Wilson
Lake contain G10 concentrations ranging up to 10 per cent, for instance,
although no kimberlite source has yet been found.
An interesting trend was apparent in the Buffalo Hills region of Alberta,
where Ashton has discovered more than 30 kimberlites over the past several
years. Over the southern portion of the play, G10 garnets were generally a
rarity, while they were more common over the northern portion of the
project area. Diamondiferous kimberlites were found in both regions,
although none of the southern kimberlites were worth the effort of taking a
mini-bulk sample. Several of the northern kimberlites were subjected to
larger samples, and some produced grades of more than 0.10 carat per tonne.
Closer to home, Ashton also found promising concentrations of G10 garnets
on its own properties in the Otish Mountains region. The company apparently
found anomalies where up to 16 per cent of the garnets were classed as
G10s. In fact, an apparent similarity of the Otish garnet population with
that of the Lac de Gras region was what first attracted the company to the
area. Ashton has since turned up a kimberlite with a promising diamond
count. The Renard-2 kimberlite yielded 145 diamonds from 163 kilograms of
rock. That included 29 macros, five of which were longer than 0.5
millimetre in two dimensions. Three of them were large enough to remain on
a one-millimetre screen, which suggests that the kimberlite might contain
an array of commercial diamonds.
It is such a find that Majescor and BHP now hope to equal or surpass, and
the partners are expected to firm up a significant number of drill targets
through ground work this winter and spring, and it seems certain that the
Portage play will see drills turning in the coming months. Whether Majescor
can turn its G10s into diamonds remains to be seen, but the market
continues to be hopeful. Indicator minerals and the Ashton diamonds
propelled the stock from 50 cents in November, to a high of $1.64 by the
end of December. Majescor hit a new high Monday, at $1.75, before closing
up 12 cents, at $1.62. |
