Author Topic: When Diamond's Began...  (Read 1698 times)

Offline Dresden

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When Diamond's Began...
« on: April 17, 2016, 09:22:02 PM »
Hi Everyone!

Okay, so, it was one of those nights a few nights ago when there was no way at all that I was going to get to sleep, 1am ticked by and was still VERY awake, among many things that were on my mind from the day ( it was one of those stressful ones) I was totally thinking about Diamonds, funny that  ;D ;D ;D I was thinking about the beginnings of Diamonds all those many, many years ago...and I really got thinking about allsorts of things. and so here are the more interesting questions/queries I had, since I am no expert, maybe some experts out there will have some kind of answers  :sultan:

1st query...okay, so, when Diamonds formed all that time ago...did they just form from carbon, such as old matter, like, hmmm, does that mean like plants, trees, or dinosaurs??? See, really I have no scientific idea at all  ;D

2nd query...is every Diamond the same age as another??? Did they all form around the same time? It seems to me that diamonds really only seem to be mined in really hot or really cold places, Argyle is hot, Africa is Hot, Canada is Cold...any reason for this?

3rd Query...If Diamonds are soooo old, then does that mean that no 'new' ones are forming and we are only finding what nature made sooo long ago?

4th query...Why are some Diamonds large and others not, some form small chunks while others large chunks...and why and how did some form colorless and others fancy colored, I know its to do with trace elements etc but maybe we will never know exactly why some form large and others not so large.

 :pear: :pear2: :radiant: :heart2: :princess:

and the queries continue... ;D


5th query...The HPHT Diamonds, the ones that are natural earth-mined Diamonds, that are type specific, I forgot the type but I think they are 1% of Diamonds mined or something like that anyway...what makes these diamonds so different that they are able to be processed to colorless and near colorless gems and fancy colors, its something to do with them being 'immature' Diamonds, they had not reached their full potential while they were forming...I think these diamonds are very interesting...

Are all of these Diamonds a light brown color or are they other colors before they are given high pressure and high temperature treatment? So could some people be walking around with these light brown diamonds, that are potentially able to be transformed into potential D/IF Diamonds without even realising? So, what color do they start out being to be processed into fancy color ones? Is there a certain location these particular diamonds are found?


That's enough for now  ;D

Happy Diamond days!

Offline oldmancoyote

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Re: When Diamond's Began...
« Reply #1 on: April 18, 2016, 04:50:23 AM »
1. It's perfectly possible that some diamonds formed from matter that at some point was organic, but there is no way of telling. The way diamonds form on Earth is quite different from most other minerals and gems, because they require pressures and temperatures that are found in a layer of the Earth known as the mantle, which starts about 50 km below the surface. Surface materials - including those containing carbon - get "recycled" through the mantle thanks to continental drift, but by the time the surface material has reached the mantle through crust subduction and the process of diamond formation can begin, all traces of the origin of the carbon has been lost (and there's plenty of inorganic carbon around!)

2. No, they are not all the same age, though as far as I know the most recent ones are about 150 million years old. The reason why they are in hot or cold places is partly chance, and partly that what we call "hot" or "cold" is actually quite normal for Earth climate. Truly temperate zones are relatively rare, and at the moment it seems none have the right geology (though Cape Town is actually not bad).

3. Probably there are diamonds forming under your feet (or mine) in this very moment, but you need a set of interesting circumstances to make them available: namely, a deep volcanic phenomenon that makes the materials of the mantle come close to the surface. This is generally not a "film" volcano, spewing lava all over the place, but a much gentler phenomenon that leaves the volcanic pipe buried... which then needs several tens of millions of years for the ground above to rise, erode and become accessible to mining activity.

4. Size is a consequence of the conditions around the crystal remaining stable for relatively long periods of time - so it's a relatively random phenomenon. This is true for diamonds as for other minerals, even home-grown crystals of copper sulphate or sodium chromate (which I used to make as a kid), though I don't know if anyone has figured out the growth rate of natural diamonds in Earth-like conditions. Colour is also a function of the environment - producers of synthetic diamonds have found that nitrogen favours faster growth, but also gives a yellow tint to the stone (one of the reasons why large "tinted" diamonds are more common). In very broad terms, boron is responsible for blue, hydrogen for violet, green is the effect of radioactivity and the family of red to brown colours is caused by deformation of the crystal lattice (but brown can also arise from other causes or a combination of those above).

5. HPHT is used for a number of purposes - among which that of altering colour, in which case (usually) there is an addition of nitrogen to faint yellow diamonds to make them become brighter yellow. What you are referring to is an HPHT treatment to improve clarity as well as colour, and basically it works by heating the diamond so much that the crystal lattice becomes "fluid" again, and it can release the tension causing the brown colour, thus making it disappear (and/or allowing nitrogen clusters that cause "yellow" to disperse). Not all browns are suitable, because not all browns are "lattice strain" diamonds. Many browns from Australia are of this type, but not all, and vice versa not all diamonds suitable for HPHT treatment are brown or from Australia - for example some yellows (and pinks - though it's unlikely they would be turned into whites!) are not from Australia but are suitable for HPHT.

This is a brief summary. Probably the ultimate text on coloured diamonds is Stephen Hofer's Collecting and Classifying Coloured Diamonds, which is the source of much of the above information. Unfortunately it's out of print and quite expensive, but a good library should have a copy.
« Last Edit: April 18, 2016, 04:58:10 AM by oldmancoyote »

Offline oldmancoyote

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Re: When Diamond's Began...
« Reply #2 on: April 18, 2016, 10:13:04 AM »
Actually, it turns out I was wrong about #1:

Quote
Through studies of carbon isotope ratios (similar to the methodology used in carbon dating, except with the stable isotopes C-12 and C-13), it has been shown that the carbon found in diamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction (see plate tectonics) before transforming into diamond. These two different source of carbon have measurably different 13C:12C ratios.

Source: https://en.wikipedia.org/wiki/Diamond#Natural_history

Offline oldmancoyote

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Re: When Diamond's Began...
« Reply #3 on: April 18, 2016, 12:27:19 PM »
...and it seems I need to be more precise about #2 as well:

It is absolutely true that not all diamonds are the same age, however the range depends on how you count "age": formation of the actual diamonds found today took place somewhere between 3.3 billion and 900 million years ago. Transportation of the diamonds to the surface through volcanic pipes is much more recent, and what gave rise to the paltry number of 150 million years ago (and in fact the Panda kimberlite in Canada is dated to about 50 million years). It looks like the oldest found pipes are about 1.2 billion years old.

See http://www.gia.edu/gems-gemology/spring-1991-diamond-emplacement-kirkley (though this is old, further studies carried out as late as 2013 seem to confirm the data: http://www.gia.edu/gia-news-research-tiny-inclusions-reveal-diamond-age )
« Last Edit: April 18, 2016, 12:35:16 PM by oldmancoyote »

Offline Dresden

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Re: When Diamond's Began...
« Reply #4 on: April 20, 2016, 09:51:30 PM »
Great post OMC - Thanks!

Very interesting to read all that. so that means some Diamonds are older than others, I wonder if that means they are any different structurally from one another, the older and newer ones? would that mean the older ones are more ''tougher'' structurally - as in less prone to chipping etc...would be interesting to know.

GOSH these Diamonds are old  ;D :D ;D JUST AMAZING THEY ARE...WOOWZA!


AND...back to those HPHT ones...does that mean the ones that are processed into colorless/near colorless ones start out as light brown and they have to have high clarity right? what about the fancy color ones, what color do they start out as, such as a fancy pink what color would that have been before it was HPHT processed So nothing is added to the Diamond right, its just HIGH PRESSURE AND HIGH TEMPERATURE, like returning them back to where they came from to go back to work?  ;D

So I see that GIA does grade these ones processed by HPHT so I guess it still means they are no way close to ever having the tag of being NATURAL FANCY COLOR / COLORLESS/ NEAR COLORLESS Diamonds...so it will always mean they will never be as treasured or as sacred as the real thing...but I assume it means they are more sacred than the irradiated ones?



If only these Diamonds could speak and tell us the full story  ;D

Offline oldmancoyote

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Re: When Diamond's Began...
« Reply #5 on: April 21, 2016, 05:45:18 AM »
Hardness is more a question of how regular the growth has been than age itself - and the amount of pressure in the growth environment (under extreme pressure, carbon forms into lonsdaleite, which is even harder than diamond; under low pressures you tend to get multi-crystalline diamonds, or at least this is what tends to happen in some synthetic growth technologies).

I don't think that high clarity is a pre-requisite for HPHT treatment; I suspect it's more a question of the type of inclusion (e.g. strong internal graining is OK; a big feather is probably not), but I'm not an expert. In terms of "nothing added", it depends: if you are trying to change colour to get a stronger yellow, there is something added; if you are trying to remove brown and go colourless then nothing added.

HPHT processing with current technologies is relatively reliably detectable; however, as in any other gem treatment area there is an arms race between the treaters and the detectives, and there are constant rumours of "a new, undetectable treatment". Joseph Bramah's lock resisted picking for 67 years, but would not be considered a high security lock now...

If diamonds could speak and tell us the full story, they'd probably say "Ow, that hurt". 1200 C and 55,000 atmospheres of pressure are not a pleasant environment.

Offline Dresden

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Re: When Diamond's Began...
« Reply #6 on: April 30, 2016, 07:44:04 AM »
Hi everyone!

and so it was another of those nights the other night, thinking of Diamonds way past sleep time and of course sleep would not come...so I had got thinking about the cut/shape of Diamonds and the color/colors they get graded. I know with the fancy color diamonds the aim is to get the color to be most intense so generally round shape is not chosen, so I then wondered if a Diamond is cut for a fancy shape, it may get a higher color grade but will it suffer with carat weight because of trying to get a higher color grade? Its just that you do not tend to see that many round brilliant fancy color diamonds - I have always heard that rounds are more expensive as it takes more rough to cut them, I always thought a pear shape would need more rough to cut.

and then with the D-Z color Diamonds - does that also mean that a round will show less body color than a fancy shape, hence be more coveted/valued?

I also got wondering does GIA ever get it wrong, as in wrong with the color/clarity grade of Diamonds, since they are only human and humans can never be 100% perfect  :angel:

Always great words from you OMC - you have AMAZING knowledge  :)

Offline oldmancoyote

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Re: When Diamond's Began...
« Reply #7 on: May 01, 2016, 08:17:39 AM »
if a Diamond is cut for a fancy shape, it may get a higher color grade but will it suffer with carat weight because of trying to get a higher color grade?
Unlikely. Rounds tend to have the lowest yield (finished weight/rough weight) of all, because diamond crystals are "square" (well, OK, octahedral, but an octahedron is square in section), so shapes that stay close to a square outline don't need to get rid of the corners...

Its just that you do not tend to see that many round brilliant fancy color diamonds - I have always heard that rounds are more expensive as it takes more rough to cut them, I always thought a pear shape would need more rough to cut.
Not true in general. Pears (and marquises, and hearts, and ovals) are cut from flattened and elongated (distorted) crystals called macles, and there is a lot more flexibility when cutting irregular shapes. Bear in mind that if the diamond rough is big enough, two or more finished gems can be cut from it.

and then with the D-Z color Diamonds - does that also mean that a round will show less body color than a fancy shape, hence be more coveted/valued?
In general, and with a proper cut, yes: the optical path in colourless rounds is generally made as short as possible, so light doesn't have too many opportunities to "pick up colour". However, bear in mind that D-Z diamonds are graded for colour through the side, i.e. avoiding issues of light path length, so all Gs have the same body colour (or rather, have a body colour that is between F and H. There will be differences!)

I also got wondering does GIA ever get it wrong, as in wrong with the color/clarity grade of Diamonds, since they are only human and humans can never be 100% perfect
Oh, yes, they do, particularly with colour on fancy colours.

Offline Luriya

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Re: When Diamond's Began...
« Reply #8 on: June 16, 2016, 11:39:19 AM »
Yeah its amazing that a type of mineral can make people rich. Sell diamond jewelry and you can make some good money
« Last Edit: June 17, 2016, 03:33:14 AM by oldmancoyote »