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Trigons

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Iceman

Brilliant_Rock
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Aug 25, 2000
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Here is one of "my 8000" posts that they deleted on DT. I think its their educational loss. I have never seen so many trigons on one diamond in my life.

Enjoy the picture you wont see one like this !

trigons1.gif
 

Giangi

Ideal_Rock
Joined
Jan 23, 2003
Messages
2,530
What a great pic, Ice! Did you take it?
 

Iceman

Brilliant_Rock
Joined
Aug 25, 2000
Messages
1,374
I took the picture and wish I would have kept the diamond

Ive looked at a lot of diamonds in the last 25 years and never came across this. Also the cameras are better now, not like what I used back then.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,271
Wow! Talk about making full use of the rough! Nice shot Ice.

Rhino
 

Rank Amateur

Brilliant_Rock
Joined
Feb 26, 2003
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1,553
Yeah! Great trigons! Look at those! Whoowee!

Wait a minute.

What the **** is a trigon?
 

mike04456

Brilliant_Rock
Joined
Nov 20, 2002
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1,441
Trigons are a surface feature of many rough diamonds. There is some disagreement about how they are formed, but most geologists believe they occur while the diamond is being brought to the surface in the kimberlite, when the hot magma causes dissolution of the crystal.

They are important because they tell you where the octahedral face of the crystal is, which is crucial for cutting correctly.

A bit more here:

http://www.amnh.org/exhibitions/diamonds/trigons.html
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Trigons are generally considered to be a product of crystal growth. Certain parts grow faster than other. The slowest growing part is the Octahedral face. Trigons are a selection of the faces that have lagged behind.

Wayne
Melbourne Diamond Exchange Ltd
 

mike04456

Brilliant_Rock
Joined
Nov 20, 2002
Messages
1,441
Wayne, I don't know who told you that, but that's not the general consensus as I understand it, at least not in the geologic community. I checked some of the authorities in my reference library, and they all refer to trigons as being "etch features," i.e., cavities formed by natural etching during emplacement. The jury is still out on this for obvious reasons (no one has observed diamonds being emplaced since the last one was brought to the surface millions of years ago) but I've not seen any scientific authority refer to them as simple crystal growth structures.
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Hi Lawgem
I think what you may be referring to is an “Etch Pit” geologically described as “ An indentation on the face of a diamond crystal that was partially dissolved during growth”
This is where is there is sometimes a bit of confusion in identification,
“Etch pits are triangular on octahedral faces. Boat shaped on dodecahedral faces and square on cube faces, They are also sometimes called etch figures

Trigons on the other hand are described as “ Triangular indented growth marks found on the octahedral faces of a rough diamond and sometimes on naturals. It is usually, but not always, oriented opposite to the crystal face on which it appears.”

By the way Lawgem any interesting data you may have regarding etchings or the composition of inclusions would be appreciated.

Wayne
Melbourne Diamond Exchange Ltd
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Hi Lawgem
Forgot to mention, If you have an interest in the subject we would be happy to include you in correspondence relating to our research into resorbed crystal forms of Australian origin. We have up to now catalogued and named 109 shapes from 9500 crystals. The research is looking into their formation, eruption and the subsequent histories that moulded their forms.

Regards
Wayne
Melbourne Diamond Exchange Ltd.
 

mike04456

Brilliant_Rock
Joined
Nov 20, 2002
Messages
1,441
Wayne, what's the reference you're quoting from? I'd like to take a look at it. From my reading, I've seen geologists using the terms "etch features" and "trigons" interchangeably. I wasn't aware--or at least, I have not come across such before--that there was such a clear distinction between the two. Do you have this research of yours archived or published anywhere or it is proprietary?
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Hi Lawgem
For the sake of easy cross-reference I quoted the definitions from the GIA diamond dictionary.
The research is by our Dr Julian Hollis and is not yet completed and relates to Etching – Resorption Histories. A section of the work has recently being published in The Australian Gemmologist Vol 21 Number 9 entitled Morphology of Bingara Diamond Crystals.
You can see a bit of the research on our website at http://www.diamondexchange.com.au/GeologyP1.html ( Sorry about the link Leonid but it is educational not commercial He He )
What could be of interest to the industry as a whole is the possibility of creating a standard for grading rough diamond shapes. At this point we have catalogued and named 115 shapes from inspecting 9500 rough diamonds. I would be happy to send you copy of the drawings that you may contribute your findings.

Dr. Hollis will soon be producing a cross reference chart entitled “OFERCIPAS: An interpretation of causes of surface features on Monte Christo diamonds”

Hey Furthermore how about contributing some Brazilian rough, Does not need to be larger than 0.10cts as we are using an electron microscope. We just need them for about 3 weeks

Wayne
Melbourne Diamond Exchange Ltd
 

mike04456

Brilliant_Rock
Joined
Nov 20, 2002
Messages
1,441
The Diamond Dictionary?? Good grief--it was GIA authors I was referring to in my previous posts about using the terms interchangeably. I checked my copy and you're correct on those definitions. I wonder if they are getting obsolete based on more recent publications, or if the current authors are just sloppy. Clearly more reading is in order here.


Thanks for the references. I'll check them out. The crystallography of diamonds is fascinating and there is so much more to learn about them.
 

pyramid

Ideal_Rock
Premium
Joined
Nov 10, 2002
Messages
4,607
I think it was in the book 'The Nature of Diamonds'(by George E. Harlow)that I read that trigons would usually have an inclusion behind them. I think I asked about this onetime on a forum though and was told it was not true. Does any of you know?
 

pyramid

Ideal_Rock
Premium
Joined
Nov 10, 2002
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4,607
Okay, it was not in that book. I cannot find my copy but I looked up amazon and it just so happened that where it lets you look inside the book I could see the pages about trigons. It must have been on another newsboard that I read this. Anyway does anyone know if it is true?
 

valeria101

Super_Ideal_Rock
Premium
Joined
Aug 29, 2003
Messages
15,809
That's the side of a princess 'cut' ? Nice polish
 
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