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RI testing of microgems


#1

What is the smallest crystal which can be reliably tested for RI?

With respect to microdiamonds specifically, see
http://www.minsocam.org/MSA/collectors_corner/arc/diamondm.htm


#2

Hello Orchid:

Penelope Paydirt here… not to be confused with my evil twin
Penelope Dirtbag at Chilliwack Rockhounds who used to post to this
list.

What I am researching is a way of testing for microminerals in field
gemology when the task is truly like the proverbial needle in the
haystack and it is a problem I have presented to Senator Neufeld,
cc’d and those he uses as advisors. I worked in NWT gold mines where
most of the gold was microscopic but the “big three” of precious
gems are perhaps 100x less concentrated than gold. If only I had
anticipated the diamond discoveries when I prospected that region in
the 60s I would have taken appropriate samples and done the
crystallography profiling… if it was affordable of course. How
then do prospectors working the clays of NE Alberta for diamond
finds today test their theories and practices?

If we can discover “vectors” of microminerals in the field, they may
point horizontally or vertically. Yes, vertically as I have seen the
theory (plausible) that some platinum deposits here may come from the
sky… but then the science establishment before Cuvier in the
1800s said rocks cannot come from the sky. Was Blue in 1900 wrong
when he reported to the Ontario Minister of Mines that he thought
there were diamonds in shale-slate types of rocks? Did those
kimberlite pipes and vents ever blow out microdiamonds which landed
in loose sediments destined to become mudstones, shales and slates?
Blue’s diamonds may come from the sky (“Lucy in the sky with
diamonds…”).

In the 50s I found two kinds of shell fish replacement fossils in
the sandstones 35 miles SW of Ottawa. I could probably guide anyone
to the area today online if they are interested in a followup.

The quartz crystals were up to 2 mm across. But then we all know the
expression, “as soluble as glass”. Does anyone know of lab solubility
testing for glassy micromineral crystals which might be helpful to
prospectors?

Do diamonds, sapphires and emeralds dissolve in some powerful
chemicals? Are there solubility differentials which can be
diagnostic?

Even with the limited microscopes we have here, we can isolate
microminerals which are invisible to the naked eye. Honestly I am
"dazzled" by the displays I see sometimes from reflection and
refraction. So much so that I am seriously thinking of taking the
previously helpful advice from Orchid contributors on
photomicroscopy even though I don’t know how much diagnostic power
there is in photos of microminerals at 100x magnification or more.
Sometimes it LOOKS to me like I am seeing diamonds, sapphires and
emeralds in the microscope but I am very limited in microscopy.

Can these miniscule microcrystals be weighed reliably and tested for
SG and solubility? If so, down to what size/weight?

If we had affordable and reliable RI plus SG plus solubility data on
nano or micron sized microminerals we might have the problem solved.

PP
cc - PD at Chilliwack Rockhounds


#3

Yo, Penelope Paydirt here.

Try, try again as my evil twin, Penelope Dirtbag says.

Our “Microminerals” business has one gram samples of dust and grit
from two mineral properties for micromineral assay. Conventional
assays will not suffice. In the longer term we need a
CRYSTALLOGRAPHY PROFILE, not a profile of elements.

But let’s start with one sample of one gram and the determination of
one type of crystal. The dust-grit size ranges mostly from 1 to 100
microns. It contains some stunningly green crystals. Are they
emeralds, green sapphires or other? If you were prospecting and found
one gram sized crystals like these a few mm wide you would be very
impressed and you would rush to make a conclusive determination. Why
not the same enthusiasm for micron-sized crystals?

Let’s start with an assay of these green crystals. The mining
authorities have said that we can use such unconventional assaying
expenses toward “claim maintenace costs”. The only qualification they
have given so far is that the person doing the determination must be
"professional".

Please send details of cost etc. off-list and we can take it from
there. We will argue for the professionalism of an accomplished
jeweller/crystallographer anywhere on the planet if you have the
record of success even if there is not one piece of paper you can
hang on the wall to prove “professionalism”.

The two mineral properties are over a volcanic field which may be
fed by the same magmas which feed Mount Baker in Washington State.
They are on the side of what seem to be smaller “volcanic cones” and
close to major fault lines. The rocks are designated on geological
maps as a mixture of igneous rocks (like andesite) and metamorphic
(ranging from slates to amphibolites). There are fossils locations
shown on the geological maps.

Senator Neufeld is cc’d again because of the standing question as to
whether the crystallographer at Ottawa’s National Museum could make
this determination and then answer the broader question of how to
arrive at affordable profiling for microcrystal (vs. microelement)
determinations.

It is difficult enough prospecting for precious gems which are 100x
less concentrated even in economic deposits than gold at 1/10-1/20 oz
per ton. But the problem of quick and affordable assaying adds
greatly to the difficulty. Is it solvable?


#4

OK, having been perplexed by this Lazarusian thread I have to
ask…why?

I’m not being facetious, I just don’t get it. Is there a market for
gem dust?


#5

To answer the first question posed in your posting- "why not the same
enthusiasm for micron sized crystals? BECAUSE THEY ARE WORTHLESS per
se. There has been an awful lot of mission creep in your postings
Peter, from diamond deposits to looking for rubies and emeralds. To
answer the second question you need to do either XRD or quantitative
x-ray analysis on you samples. Going back to diamonds, I told you
how to separate the wheat from the chaff using settlement (or a heavy
liquid separation).

Go to your nearest university with a geology/materials science
department and they will do the determinations you require. I
suggested this over a year ago but you havent progressed this. Are
you afraid of the answers analysis will give you? There is no future
in your prospecting unless you know the source rock location as what
you have is valueless.

Nick


#6

I appreciate the replies from all parties given in the past year. I
read every one and make notes.

The answer to my main question about “crystallography profiles” (for
want of a better expression) which are as affordable as conventional
assays, so far the answer is NO. The best I can find is at Acme Lab
in Vancouver (Googleable) the following under “Geochemical Whole
Rock Major and Trace Element Analysis”

Acme will work with .1 gram samples and give back a profile of 11
mineral oxides.with lower limits usually of .01% and upper limits of
100%. This plus a few others which includes C (organic + inorganic I
assume) in a 20 parameter profile for an affordable $26.70. So that
is Group 4A, “Whole Rock by ICP”.

Now 4B (Total Trace Elements by ICP-MS) requires .6 grams but it
yields a profile of 45 elements including Be.

I just gathered 500 lbs of samples and guestimate they contain about
1,000 tiny “intensely” green crystals, some quite transparent and
some more opaque. I’ve seen a lot of local jade and crysoprase and
neither is even close in being as intensely green. The largest is
about 1/10 mm. With a lot of painstaking work, I could isolate these
1,000 crystals with some of the matrix still clinging. So let’s say
I end up with 2 grams of which 90% is matrix. Acme can assay it as
above. What use is that Correct me if any of the
following is in error:

If I have green sapphire then I expect high Aluminum Oxide.

If I have green emerald then I expect a high Be assay.

With all due respect for those who have posted that dust-sized gems
are of no value, I disagree and IMO their error is because they are
gemologists but not prospectors. If I end up with proof that these
little gems are either sapphire or emerald then I expect the mineral
properties for this entire end of the Fraser Valley will be claimed
by the big mining companies. Likewise for diamonds.

But I do not think the Acme assays on their own are very close to
complete proof. So let’s say I follow up the Acme assays with sending
samples to a jeweller like yourself for RI and other tests like SG
and solubility and do get that complete proof. But first I would have
to know the tests.

What I have not been able to get a direct answer on is the size of
INDIVIDUAL microminerals which can be determined by a skilled
jeweller.

If I send you one gem in the “micro” range, ie one microgram and one
micrometre can you determine if it is diamond, sapphire or emerald?

If I send you one gem in the “nano” range 1,000 times smaller can
you do the same?

Granted you are not going to see these gems at Buckingham Palace.
You only going to see them in the crown jewels of Lilliput or maybe
the British Museum in London which I quite enjoyed, including the
entire oil rig from early days of oil mining. Remember Daniel Day
Lewis who won an Oscar for his performance in “There Will Be Blood”?
When he switches from silver prospecting to oil he is first
laboriously hauling buckets of goop to a storage pond. This is a
digression except that quick and cheap methodology which opens BC to
microgem prospecting and mining on a big scale might well get a
display in the British Museum.

From the standpoint of marketing, imagine a display in a downtown
Vancouver jewelry store with a projector and good resolution
equipment diplaying local emerald or sapphire microgems from a
display case onto a screen. Outside on the sidewalk there is my bad
twin and bag lady Penelope Dirtbag from the Vancouver Stock Exchange
with an organ grinder and a monkey selling shares in the Dirtbag
Mining Company. “Brother Can You Spare A Billion”? Us Dirtbags like
to think big.

If I find gold dust on the bar where River A meets River B that
points to gold upstream. That is its value. And it IS value even if
we do not know which stream at first.

Now as for my tiny micromineral crystals which may be diamond, I
have similar ratios of samples to material for assay. Acme assays can
determine organic C and inorganic C. But which is graphite? Is
diamond the only inorganic C?

Penelope Paydirt

PS - In high school my prospecting led to discovery of two species
of fossilized shell fish in sandstone of the Ottawa Valley. My HS chem
teacher said, Quartz is not soluble. But I had the 2 mm and smaller
quartz crystals in the shell fish to prove otherwise. I never told
her this. Her husband was an eminent PhD geologist. Maybe in those
days (50s) the theory of quartz solubility was as suspect as the
theory of plate tectonics or calaclysms in species development or
deep-dwelling microbes or the theory that some mantle rocks can end
up as huge surface formations, eg in Newfoundland. When did the
theory of micro-organism formation for microgold gain acceptance?
Even the QUESTIONS which challenge science dogmas are ridiculed at
first. Google on Yukon emeralds and read a team of eminent earth
scientists calling their etiology an “enigma”.

My HS chem teacher called water “THE UNIVERSAL SOLVENT”.

How soluble are diamond microcrystals?

Are there any micro-organisms which may ingest them, transport them
and concentrate them as is done for gold and platinum by tiny
critters?

Us Dirtbags like to think small.


#7
I'm not being facetious, I just don't get it. Is there a market
for gem dust? 

I gather that the discussion is about prospecting. Where there are
little ones, there may be big ones.

Al Balmer
Sun City, AZ


#8

Thank you Al. Nobody could have said it better in so few words.

Now as Peter Rowe commented, green crystallization could be a lot of
different minerals. Yes there is abundant calcite in the matrix
based on acid tests and calcite is associated with emeralds but the
emeralds of northern BC and southern Yukon also are associated with
tourmaline so I am looking into that as well. Three SG tests of the
matrix gave 2.7, 2.9 and 3.0.

The 1939 Ksanda and Henderson paper for which I cited a URL earlier
identified diamonds as small as 1/10 mm in rocks from the sky so I
wondered how far nano- and micron- scale assays had advanced.
Certainly when I worked in a NWT gold assay office in the early 60s
we could not do the amazing profiles of Acme today with cheap and
fast ppp results. Before Cuvier, science dogma was that rocks could
not fall from the sky and France had no balladeers from England
singing Lucy in the sky with diamonds in those days. Science
progresses and today it progresses at blistering speed.

I appreciated Mark Zirinsky’s on SEM technology and also
Bill and Karen Lechner suggesting Dr. Piilonen and Canadian Museum of
Nature. I had a hunch too that some people are so immersed in
emeralds for so many years that they will just look at a stone, big
or small, and say in a flash - That is/is not an emerald.

I have here a flake of matrix with crystals and I will send it to
anyone, no cost and no obligation except to mail it back because am
only working from an outcropping and cannot get more samples unless
we go expensive drilling and blasting. I will not send it for idle
curiosity but if anyone has some equipment to use on it, then out it
goes. It is fragile so examine but please do not damage it.

The flake is 13 mm x 5 mm x 1 mm. It weighs 90 mg. It contains about
a dozen tiny green crystals so 90%+ is probably matrix. The crystals
are mostly flat green. The transparent greens are rarer.


#9

They are quoting for XRF and ICP which are destructive tests. You
either powder, dissolve, blast with a laser or melt the samples for
such tests and with the exception of ICP which can be done by laser
ablation if a laser is coupled to the machine. You want SEM with
quantitative x-ray microanalysis (EDS) and single crystal XRD or
possibly EBSD via the SEM. IF you dont mind a destructive test them
SIMS profiling is best. Quant x-ray TEM for your 1-2 micron samples
will work well.

You will not be able to analyse beryllium as an element other than
by plasma and Atomic Absorption spectrophotometry.

Getting back to the only mineral anyone else on this planet would be
interested in, have you done any heavy mineral separation yet? This
means putting some of your sample in a suitable dense liquid and
your diamonds will sink and all the common silicates will float.
No-one is interested in green minerals of that size commercially and
without a primary source rock no-one will be so stop calling them
gems. Emerald is a form of beryl and is common in granitic rocks.
they are common even in the UK and at best are turned into railway
ballast. Why? purity, clarity and size. Sapphires dont appear in fine
sediments because hey dont get ground down in the same way as
silicate minerals. Hence me telling you to look at stream sediments.
Use a simple gold pan to sort out the heavy minerals and pick through
them under a binocular microscope to reject the pyrite, iron oxides
etc.

You can reduce your bulk samples down immensely by putting a
quantity in a bucket of water and stirring vigorously. After leaving
for 20 seconds pour way the water. Refill with water and stir gain
only pouring the water away after 2 seconds of settlement. If you can
amage i repeat and pour off water after 1 second. You will really
need a smaller container to chuck away the water after a second so
divide the sample up into managable portions. You have now got rid of
nearly all of the platy clay minerals. Still got too much sample?
then sieve some into 3 ranges- less than 38 microns, 38-60 microns
and finally coarser. the coarser ones you can see with a microscope
and pick through with a needle if you cannot get a heavy liquid
separation. (tetrabromoethane TBE is a commonly used liquid)

Your questions also suffer badly from what is known as “mission
creep”. You start off with one aim and digress badly. Yes, quartz
does dissolve by what is known as pressure solution. That is how
hyrrothermal minerals are formed. Gold is commonly in a hydrothermal
deposit so geologists look at other minerals that have similar
geothermic and geobarimetric properties such as arsenpyrite,
sphalerite and pyrrhotite. By looking at subtle changes in chemistry
of thse you can tell if you are barking up the wrong tree or not.
The same goes for platinum but here it is the amount of oxygen,
silicon and temperature that decide things. Same for diamond.

Organic carbon inthis context is carbon in carbonates (limestone)
Inorganic carbon is everything else including graphite and diamond.

The British Museum wont be having a display of microgems because
colour is seen from the absorption of light of differing
wavelengths. When objects get down to a certain size everything looks
black. People would not be impressed with a display of black mud.

Now, the above I have communicated to you before but you still dont
seem to have even started sorting your material out to any useful
degree and then you google the wrong thing when I told you what
techniques to use and where to ask. Please, for the sanity of some
of us follow up what has been suggested and report back on that
rather than continuing with these rather long taradiddles.

I look forward to hearing about your results when you have them but
I would be pleasedif you took a little more time to understand what
is possible and what is practicable in your endeavours and set
yourself a realistic goal. As I said microdimonds might be
economically viable, microgems are a misnomer and a fallacy.

Best regards,
Nick Royall


#10

In a geology book I recently saw a microphotograph of a microscopic
piece of gold CREATED BY A MICROBE.

I might have expected it to be cubic but it was a spiral.

If it was deposited a long time ago it is a fossil is it not?
“Fossil gold” makes as much sense to me as “fossil fuel”, ie fossil
coal or fossil C.

I assume the spiral could also have been a replacement fossil in
which the gold (eg in heated water) replaced an intracellular microbe
structure.

Does anyone know if there are other photos of fossil gold? Maybe we
could have a micro-paleontology search for BC’s “official fossil”.