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Hey Dave- An OEC/OMC question

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Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
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4,924
Dave, do you use the AGA cut charts when grading the cut on Old European Cuts and Old Mine Cuts?

I've started using your cut grade system in my appraisals over the last six months or so. Very helpful, especially with dealers. They don't tend to argue so much about the grade once they see there is definitive cut grade parameters.

What I'm wondering specifically is this-

Every once in a while I'll enounter an Old European Cut which has a great "look", but falls in the 4A or 4B category. Prior to using your system, I graded cut on my own scale of Exceptional, Very Good, Good, Fair & Poor, sometimes using split grades. A stone like this I might have graded with a "Good" or "Good to Very Good" cut, followed by the comment "in context of era cut". Using the AGA system, the stone would fall in the "below average" category.

How do you handle this? Do you make a comment regarding it, or grade the OEC's any differently?

Rich, GG
Sarasota Gemological Laboratory

PS- You might find it interesting that my "instinctive cut grading" seemed to closely follow your AGA parameters. When analyzing my instinctive grading against your charts, it seemed to correlate like so:

Exceptional................1A
Very Good to Exceptional...1B
Very Good..................2A
Good to Very Good..........2B
Good.......................3A
Fair to Good...............3B
Fair.......................4A
Poor.......................4B
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
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6,399
I have a specific chart for old Euro cuts that I do not publish. I like people to be a little blind about what I sell....Make it hard for everyone else and keep it easier for me...:))

I will email it to you as a .doc or adobe acrobat file on Monday...

Anyone else wanting this may ask and I'll send it to them, too.
 

Tarams

Shiny_Rock
Joined
Nov 26, 2001
Messages
228
Rich, Dave,

I'm trying to use Dave's chart for fancy cut stones, but my specs come up in different areas. How do you determine a stones class if it falls in different ranges? This is what I come up with:
Table is 58%, so that's Class 1A.
Crown height I don't know yet.
Girdle Thickness is Medium to Thick, so that's the Class 1A-2A range.
Total Depth is 69%, so that falls in Class 3B.
L to W ratio is 1.786, so that's in the 1A-2A category.
and polish/symmetry are Good/Good so thats 2B/3A (?).
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Tarams, the rules for determining cut grade are on Dave's site as well. How you figure out the "overall" grade from the "individual" grades of the different characteristics.

The crown height would be necessary for a "complete" grade, but from the info you've given, your diamond (probably) falls in the 3A category, which is a good commercial cut. A very respectable grade, with a good appearance.

Rich, GG
Sarasota Gemological Laboratory
 

Tarams

Shiny_Rock
Joined
Nov 26, 2001
Messages
228
And you too!!!

Rich, I checked Dave's site again & found the info. Sorry I didn't see it before, but thank you for sending me in the right direction :))

GiGi, what happened with that setting you were considering?
 

GiGi

Rough_Rock
Joined
Oct 8, 2002
Messages
87
That one is a lovely setting, but does not have the simple, unique and elegant "line" look I was hoping for to complement my emerald-cut stone. I decided to go with a simple basket-prone setting for now. When that special semi-mount that tickles my fancy comes througg, then I will re-mount the stone. :)
 

fire&ice

Ideal_Rock
Joined
Jul 22, 2002
Messages
7,828
----------------
On 11/2/2002 7:58:08 PM

I have a specific chart for old Euro cuts that I do not publish. I like people to be a little blind about what I sell....Make it hard for everyone else and keep it easier for me...:))


----------------


Dave, this chart has been helpful. I hope I thanked you for sending it.
 

Beth

Shiny_Rock
Joined
Aug 2, 2003
Messages
267
Oldminer, if you don't mind, I would also be interested in that chart of yours. My email can be found in my profile.

Also can anybody direct me to further information regarding measurement of fire by cut paramaters for the older cut stones and perhaps the best most reputable places to start looking for them seriously? PM if that is more appropriate.
Thanks a bunch,
Beth
 

valeria101

Super_Ideal_Rock
Premium
Joined
Aug 29, 2003
Messages
15,809
----------------
On 11/2/2002 7:58:08 PM oldminer wrote:

I have a specific chart for old Euro cuts that I do not publish. I like people to be a little blind about what I sell....Make it hard for everyone else and keep it easier for me...
)

----------------

Not that I would particularly mind receiving the file... but this is so funny said aloud! Actually, one (elusive) thread today mentioned that some poor OMCs were tested against the HCA ?!? For what I know this should clearly not work... since the HCA starts with hard assumptions on symmetry and "finish" (not to go as far as to say facet pattern and relative proportions) that OMCs do not observe. Right or wrong?

One word would do for an answer. I was rather puzzled by this attempt of HCA usage...
 

fire&ice

Ideal_Rock
Joined
Jul 22, 2002
Messages
7,828
----------------
On 1/27/2004 5:33:29 PM valeria101 wrote:

----------------
On 11/2/2002 7:58:08 PM oldminer wrote:

Actually, one (elusive) thread today mentioned that some poor OMCs were tested against the HCA ?!? For what I know this should clearly not work... since the HCA starts with hard assumptions on symmetry and 'finish' (not to go as far as to say facet pattern and relative proportions) that OMCs do not observe. Right or wrong?

One word would do for an answer. I was rather puzzled by this attempt of HCA usage...----------------

It's not one elusive thread. I have mentioned this *many, many* times about my OEC & HCA. No one has ever discounted that fact that the data would not work for HCA.

If so, I, for one, would like to know.

I have the chart that Dave is referring to. It's an excellent resource - but basically uses the current cut grade in terms of how good one OEC is compared to another OEC.
 

Beth

Shiny_Rock
Joined
Aug 2, 2003
Messages
267
I would be interested in seeing those HCA results just out of curiosity. My theory is that the stone would perform poorly due to brilliance being the enemy of fire, but I would like to see that thread if anybody cares to direct me to it. I remember reading FIC somewhere on this site and cant find it now. Anybody know what I am talking about? Can't remember what the acronym stood for but something to do with fire and I am trying to read up on that subject right now.

I got your PM oldminer and sent you my email.
 

glitterata

Ideal_Rock
Joined
Apr 17, 2002
Messages
3,618
I wish I had that chart myself. I often (embarrassingly often) gaze deep into my OEC and wonder whether it's really a good one, or whether I just love it because it's mine. Definitely fiery rather than brilliant. But such chunks of bright color! Of course, I don't know the numbers on the stone--I've never had it appraised loose--so I guess the chart wouldn't really do me any good.

I think the polish on my OEC must not be very good, because the colors are sort of stripey, if you know what I mean. Experts, does that sound reasonable? Or is the stripey effect just part of the prismatic rainbow thing you get from refraction?
 

valeria101

Super_Ideal_Rock
Premium
Joined
Aug 29, 2003
Messages
15,809
----------------
On 1/27/2004 5:54:56 PM fire&ice wrote:
It's not one elusive thread. I have mentioned this *many, many* times about my OEC & HCA. No one has ever discounted that fact that the data would not work for HCA.
----------------

Neither do I, Fire&Ice. I have not spent all that much time here (and been lazy about reading past threads) so you latest mention of this has been the first I ever saw. I ignored completely that this issue has been tackled before. I surely appreciate your explanation
 
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