I didn''t realized I didn''t know so much until I found PS...

[lonebrave]

Ok, so you may have seen my first post here. Much thanks to those who've helped already.

Well, I spent a good portion of last night and today reading through the Tutorial and other links around PS and off on some linked pages. I thought I had a good grasp of the 4 Cs and whatnot, but I'm realizing there is just so much I didn't know or think about before.

4 Cs
Cut is most important for a good looking diamond.
Does more "sparkle" always mean a better cut?
Size affects cost the most.
Color is more forgiving than I expected, although, I need to go look and compare some stones side by side to see how well I can tell color.
Clarity, well, depends on what the inclusions are.

H&A
I didn't know anything about it until I happened into a HoF dealer, so I started researching last night. Branded seem to carry a decent markup, based on what people are saying around here. A perfectly cut stone should show H&A; it is an indication of perfect symmetry in the stone.

H&A viewer vs Ideal Scope
Ok, so H&A viewer doesn't show leakage. I understand how the Ideal Scope works, but not how this works. How is it different in function?
Ideal Scope doesn't show hearts (I thought I read that somewhere). The redder the better, except the arrows should be grey/black. Pink and white indicate light leakage

Lighting
How do the different types of lighting affect a diamonds appearance (sun/natural, fluorescent, incandescent, etc)?
One of my biggest fears is that I'm been shown something in a "favorable" lighting condition at a B&M and it's masking/enhancing something abnormally.

B&M vs online
I'm comfortable purchasing online, however, I like being able to touch and feel while I'm learning and figuring out what we want. Once I figure that out, I'll give the local guys who I really like a chance to compete against the online shops, taking into consideration care and service.

Other stuff:
Spread is a ration of the depth to diameter. An ideal stone will have a spread within the 56-65% range.
Brilliance refers to the brightness and contrast of a stone.
Fire refers to the stone breaking light into rainbow, prism like.
Scintillation refers to the intense (black and white?) sparkles in stone.
A girdle should be: thin, medium, or slightly thick
The culet should be: pointed, very small, small or medium
A stone should have ideal/excellent polish and ideal/excellent/very good symmetry.
Glare can hide light reflected through the stone from the viewer; it is ever present and good, but not dependent upon cut of the stone.

So those are my thoughts, questions, and understanding as it is now.

Please comment and correct on anything you see necessary. I greatly appreciate it.

I'm always willing to try to learn more, so any pointers to more information is always accepted. I'm trying to learn and understand as much as I can right now!

 

[lehcarm]

Wow! For only looking around for a few hours you have learned a lot! Every person new to PS should read your mini-tutorial!

I don''t really have much to add, but I just had to comment. Keep us posted on any stones you are looking into!

 

[lonebrave]

Yeah, when I said I spend a good portion of last night and today looking around, I meant it. I always learn better by writing things down; it makes me collect and organize my thoughts.

I''ll be sure to update as I learn more.

I think we''re going to go look at stones this week and next with the purpose of trying to decide what our acceptable limits are and then I''ll start looking for the stones to buy. I''m sure I''ll be back here asking many more questions and opinions.

Once again, much thanks to everyone around here for keeping such a great resource online!

 

[Regular Guy]

Date: 12/11/2006 4:34:08 PM
Author:lonebrave


H&A
I didn''t know anything about it until I happened into a HoF dealer, so I started researching last night. Branded seem to carry a decent markup, based on what people are saying around here. A perfectly cut stone should show H&A; it is an indication of perfect symmetry in the stone.

Some relative controversy on this. You may find equivalent performance without H&A. Likewise, H&A does not guarantee excellent performance. But...H&A in itself, is a good thing in a round. Still, it doesn''t leave you free to ignore proportions, otherwise.

A stone should have ideal/excellent polish and ideal/excellent/very good symmetry.

Reverse the priority...so although vg symmetry could be OK, you could have worse polish. Frequently these do travel together.

Minor notes above...excellent work! (especiallyt on the other stuff).

Good shopping!

 

[JulieN]

Spread is not a ratio of diameter to depth. Simplistically, it is a comparison between diameter and carat weight, but the high-tech defintion is a comparison between diameter of stone X to diameter of Tolkowsky-proportioned stone of equal carat weight. An ideal stone will have (more or less) an ideal spread.

You certainly do not need Ideal/Excellent finish grades to have a beautiful stone.

 

[lonebrave]

Ira and Julie, thanks for the info.

Date: 12/11/2006 7:42:55 PM
Author: JulieN
Spread is not a ratio of diameter to depth. Simplistically, it is a comparison between diameter and carat weight, but the high-tech defintion is a comparison between diameter of stone X to diameter of Tolkowsky-proportioned stone of equal carat weight.

One question, though Julie, and please correct any misunderstandings here as well. I think we're both saying the same thing, but without the details to get from one to the other, so I'll try to explain why I think so here.

Tolkowsky's formula produced a strict set of dimensions, which was later discovered to actually be a range of dimensions. You're saying that spread is a ratio of a specific diameter to diameter calculated by Tolkowsky's formula, right?

According to Tolkowsky's formula, every stone of a given weight cut perfectly should have a given set of dimensions. With a specific set of measurements, the ratios between any two of them are also finite. Therefore, there is a specific ratio of diameter to depth.

So to put a numerical value on it, it should be (I'm just picking a tolerance level of +/- 5% b/c I don't know what it should be for this calculation) 95-105% of the Tolkowsky calculated diameter for a given weight.

So, if a specific stone has a larger diameter than a Tolkowsky of the same weight, the depth of the stone must be less than the Tolkowsky to maintain the same weight. Likewise if the diameter of the specific stone is smaller than that of the Tolkowsky, the depth must be greater than the Tolkowsky.

If the Tolkolwky ratio of diameter to depth were 1/1 (100%), a specific stone of a larger diameter might have a ratio of 1.05/0.95 (110%). Both ratios, those being the ratio of the specific diameter to the Tolkowsky diameter and the specific diameter to the specific depth, would be indicate a larger spread. The inverse (smaller diameter and larger depth) would indicate a smaller spread.

(Obviously if there is a large variating in density, this would not hold true, however, I would imagine there could not be such a sufficiently large variation in density.)

An ideal stone will have (more or less) an ideal spread.

So basically, to extend this statement...
"An ideal stone will have (more of less) ideal measurements, as defined by Tolkowdsy."

You certainly do not need Ideal/Excellent finish grades to have a beautiful stone.

Good to know.

One of my weak points right now is that I have seen very little first hand. While I think I could pick out a decent stone based on the specs and calculations, I have to reference as to what a given set would look like in person. Yeah, I can look at pictures, but at the learning stage I am at, I want to be able to touch, rotate, analyze the stone myself given what all the experts say about it.

I'm planning on going out to just look at stones to get more hands on experience. I definitely have a range of characteristics to be concerned about when we go looking at stones now.

 

[lonebrave]

Date: 12/11/2006 5:20:40 PM
Author: Regular Guy

Date: 12/11/2006 4:34:08 PM

Author:lonebrave



H&A

I didn't know anything about it until I happened into a HoF dealer, so I started researching last night. Branded seem to carry a decent markup, based on what people are saying around here. A perfectly cut stone should show H&A; it is an indication of perfect symmetry in the stone.


Some relative controversy on this. You may find equivalent performance without H&A. Likewise, H&A does not guarantee excellent performance. But...H&A in itself, is a good thing in a round. Still, it doesn't leave you free to ignore proportions, otherwise.

And by performance you mean how it appears to the eye, right? Or are you referring to an object measurement of some sort?

A stone should have ideal/excellent polish and ideal/excellent/very good symmetry.


Reverse the priority...so although vg symmetry could be OK, you could have worse polish. Frequently these do travel together.

Minor notes above...excellent work! (especiallyt on the other stuff).


Good shopping!

 

[JulieN]

You make good points, but proof by contradiction:
http://www.jamesallen.com/diamond.asp?b=16&a=12&c=77&cid=131&item=882657
http://www.dimendscaasi.com/diamonds/diamonddetail.asp?src=pricescope&stocknum=6744616

http://diamonds.pricescope.com/60.asp

The crux of your (or my) misunderstanding seems to be here:
So, if a specific stone has a larger diameter than a Tolkowsky of the same weight, the depth of the stone must be less than the Tolkowsky to maintain the same weight. Likewise if the diameter of the specific stone is smaller than that of the Tolkowsky, the depth must be greater than the Tolkowsky.




If the Tolkolwky ratio of diameter to depth were 1/1 (100%), a specific stone of a larger diameter might have a ratio of 1.05/0.95 (110%). Both ratios, those being the ratio of the specific diameter to the Tolkowsky diameter and the specific diameter to the specific depth, would be indicate a larger spread. The inverse (smaller diameter and larger depth) would indicate a smaller spread.

So basically, to extend this statement...
"An ideal stone will have (more of less) ideal measurements, as defined by Tolkowdsy."
This, I meant the way I said it.

 

[Regular Guy]

Date: 12/11/2006 11:27:44 PM
Author: lonebrave

And by performance you mean how it appears to the eye, right? Or are you referring to an object measurement of some sort?

Yes, absolutely. The way the diamond looks, refracts light...gives good light performance...

On the other...though we should leave Jule to do the math for us....

Julie, in the specific example of two diamonds you give...I''m supposing the extra weight is in the upper half? where the table is bigger?

If you take the in house search, and sort by depth, the pattern is clear, and consistent with lonebrave''s point...it seems...and that typically, a less deep diamond will have a greater spread.

Likewise, deeper FICs tend to have a smaller spread.

Your 60/60 link sort of makes a different, but important, point, I think, which is Garry''s point...and that for a given depth, crown & pavilion angles critically can be very different, being more or less helpful in optimizing light performance, and so you do want to watch for that.

But...on spread...it seems it varies pretty well with depth, no?

 

[JulieN]

Date: 12/12/2006 12:36:32 AM
Author: Regular Guy

Julie, in the specific example of two diamonds you give...I'm supposing the extra weight is in the upper half? where the table is bigger?

The big tabled stone has less in the pav than the smaller tabled stone.

 

[lonebrave]

Ok, first, let me say that I really do appreciate all the help.

I hope I don''t need to say this, but certain things can be lost when discussing on forums. I''m not trying to be argumentative, but have a detailed discussion from which I can learn. I really am trying to understand as much as I can.

Date: 12/12/2006 12:36:32 AM
Author: Regular Guy
On the other...though we should leave Jule to do the math for us....

While I don''t doubt Julie knows her math (I found that page later last night), I still have the desire to understand this myself.

Date: 12/12/2006 12:00:08 AM
Author: JulieN
You make good points, but proof by contradiction:
http://www.jamesallen.com/diamond.asp?b=16&a=12&c=77&cid=131&item=882657
http://www.dimendscaasi.com/diamonds/diamonddetail.asp?src=pricescope&stocknum=6744616

I''m not sure what these two stones are suppose to disprove. They appear to be nearly identical to me.

Here is what I see.
Both stones are the same weight.
There is approximately a 1% difference in diameter.
There is approimately 1% difference in depth, however, both stones have the same depth relative to their diameter.
Stone 1 (James Allen) has a larger table than stone 2 (Dimend Scassi).
The crowns of both are identical, relative to their diameter.
The pavillion of stone 2 is slightly deaper (0.5%) relative to it''s diameter.
The crown and pavillion angles of stone 1 are larger than those of stone 2.
While the crown depths are the same, the pavillion depths are not quite identical, with stone 2 having a 0.5% greater depth than stone 1.
There is a slight difference in girdle thickness, which when taken into consideration with the crown and pavillion depths allows for the same overall depth %.

So by my formula (dia/depth)...
Stone 1''s spread = 1.6126 (6.37/3.95)
Stone 2''s spread = 1.6140 (6.44/3.99)

Both stones have a "Very Good" spread according to the HCA calculator.

What did I miss?

Date: 12/12/2006 12:00:08 AM
Author: JulieN
http://diamonds.pricescope.com/60.asp

Ah, yes, the two stones pictured on the 60:60 page have the same table, diameter, and depth. The weight is distributed differently between the crown and pavillion of each. That makes sense.

According to my statement (spread = dia/depth) these would have the same spread.
Obviously they are going to perform differently.

According to your statement, I''m not sure. I''m think I understand your definition, but I still have questions.

You definition is that spread is a comparison of the diameter of a specific stone to that of a Tolkowsky stone of the same weight. Am I stating this correctly?

How does one know what diameter a Tolkowsky stone should have? There''s a formula for this, right? I guess I need to study Tolkowsky''s work.

Date: 12/12/2006 12:00:08 AM
Author: JulieN
The crux of your (or my) misunderstanding seems to be here:
So, if a specific stone has a larger diameter than a Tolkowsky of the same weight, the depth of the stone must be less than the Tolkowsky to maintain the same weight. Likewise if the diameter of the specific stone is smaller than that of the Tolkowsky, the depth must be greater than the Tolkowsky.

If the Tolkolwky ratio of diameter to depth were 1/1 (100%), a specific stone of a larger diameter might have a ratio of 1.05/0.95 (110%). Both ratios, those being the ratio of the specific diameter to the Tolkowsky diameter and the specific diameter to the specific depth, would be indicate a larger spread. The inverse (smaller diameter and larger depth) would indicate a smaller spread.

Are you saying my logic is in error, or are you saying you don''t understand what I said? If it is in error, please show me where, so that I can better understand it. The only thought that comes to mind after looking at all the information above is that maybe I shouldn''t be using the overall diameter, but the table diameter instead.

I don''t know what to think after looking at the 60:60 information. Do the two stone pictured have the same spread or not? See below about well cut and spread being related or independent.

Date: 12/12/2006 12:00:08 AM
Author: JulieN

Date: 12/11/2006 11:20:39 PM
Author: lonebrave
"An ideal stone will have (more of less) ideal measurements, as defined by Tolkowdsy."

This, I meant the way I said it.

Your original statement was:
An ideal stone will have (more or less) an ideal spread.

Are you defining a stone with an "ideal spread" to have the same diameter as a Tolkowsky stone of the same weight? That makes sense, however, going back to my questions above, I''m still not sure how to measure the spread given only the information about a specific stone. One would have to know, or be able to calculate (based on weight alone?), the diameter of a Tolkowsky stone in order to calculate the spread of a specific stone.

Ok, let me put forth a few more thoughts running through my head...
A well cut stone will have a good spread. So if I find a well cut stone, it will have a good spread. I still don''t know how to measure spread. One might say (don''t get me wrong, I''m not trying to say anyone here is saying this, just hypothesysing) a good spread is that of a well cut stone. Obviously, it is the inverse of the first statement. But, can a poorly cut stone have a good spread? Are the two independent? Are well cut stones a subset of those with good spread?

Two other observations:
First, the HCA calculator seems to define spread as "diameter for weight" (on the results page), as JulieN stated it was.
Second, the Tutorial says (http://diamonds.pricescope.com/spread.asp):

If you divide the depth by the diameter and multiply by 100 you can calculate the depth percentage. This should be between 56% and 65%. If the table is small the depth will can be larger, and vice a versa. The smaller the depth percentage, the larger the spread. Other factors that effect spread are the girdle thickness and crown and pavilion angles."

Which I understood to say that:
depth% = (depth/dia)*100
spread & depth % are inversely proportional (spread = 1/depth% or dia/depth)


Please do help me to understand this better. I really do appreciate it.

 

[JulieN]

Because...the diameter and depth % are related.

You can only have 3 sig figs.

Stone 1's spread = 1.61 (6.37/3.95)
Stone 2's spread = 1.61 (6.44/3.99)

Because both have depth of 62%: 1/.62=1.61

All stones with x depth will have y spread by your definition of diam/depth. Right?

However, we KNOW that stone #2 has larger diameter and both are same carat weight, so they cannot have the same spread. Need new definition.

Yes?

Tolk is 59.3% depth, btw.

 

[lonebrave]

Date: 12/12/2006 7:29:31 PM
Author: JulieN
Because...the diameter and depth % are related.

You can only have 3 sig figs.
Stone 1''s spread = 1.61 (6.37/3.95)
Stone 2''s spread = 1.61 (6.44/3.99)

Because both have depth of 62%: 1/.62=1.61

All stones with x depth will have y spread by your definition of diam/depth. Right?

Assuming "x depth" is a percentage, agreed, I think.
We agree that:
depth% = dia/depth (both actual measurements)
spread (my definition) = 1/depth% = depth/dia (both actual measurements)

right?

Date: 12/12/2006 7:29:31 PM
Author: JulieN
However, we KNOW that stone #2 has larger diameter and both are same carat weight, so they cannot have the same spread. Need new definition.

Yes?

I''m not sure. A couple questions:
What definition of spread are you using in this statement?
True or False: Assuming a constant weight, given a specific diameter there is only one possible depth.

Date: 12/12/2006 7:29:31 PM
Author: JulieN
Tolk is 59.3% depth, btw.

Thanks.

 

[scarleta]

You sure have done lots of work and research good 4 you.Keep us updated ,,, Are you only considering round b cut ? good luck and keep us posted.. thanks

 

[lonebrave]

Date: 12/13/2006 12:17:24 AM
Author: scarleta
You sure have done lots of work and research good 4 you.Keep us updated ,,, Are you only considering round b cut ? good luck and keep us posted.. thanks

I''m trying to understand everything I can (as is probably pretty obvious by this thread already

). Yeah, we''re only looking at round brilliant stones.

I think I said it way up near the top of this thread (but maybe it was my other one), but we don''t have much hands-on experience with stones. Most of our knowledge it "book knowledge" from PS and a couple other sources. I have a couple jewelers brining in stones this week/weekend so we can start looking to see if what we think we''ll be happy with is actually acceptable to us.

I''ll definitely be posting pics once we get it all taken care of.

 

[lonebrave]

Date: 12/13/2006 12:04:13 AM
Author: lonebrave

Date: 12/12/2006 7:29:31 PM
Author: JulieN
Because...the diameter and depth % are related.

You can only have 3 sig figs.
Stone 1''s spread = 1.61 (6.37/3.95)
Stone 2''s spread = 1.61 (6.44/3.99)

Because both have depth of 62%: 1/.62=1.61

All stones with x depth will have y spread by your definition of diam/depth. Right?

Assuming ''x depth'' is a percentage, agreed, I think.
We agree that:
depth% = dia/depth (both actual measurements)
spread (my definition) = 1/depth% = depth/dia (both actual measurements)
right?

Date: 12/12/2006 7:29:31 PM
Author: JulieN
However, we KNOW that stone #2 has larger diameter and both are same carat weight, so they cannot have the same spread. Need new definition.

Yes?

I''m not sure. A couple questions:
What definition of spread are you using in this statement?
True or False: Assuming a constant weight, given a specific diameter there is only one possible depth.

Ok, so after thinking about it more last night and today...

Your last argument has a logic flaw in it. You are using two different definitions for spread.

That being said, I''m beginning to see the uselessness of my definition of spread (dia/depth). What more information does it provide than what we already have? None. It is just an inverse of a ratio already provided. I''m understanding the diameter to weight ratio now, however, it is much clearer when stated as the ratio of diameter to Tolk diameter as you first pointed out with your ''high-tech'' definition.

Now, I have some problems with the information in the Tutorial regarding spread (http://diamonds.pricescope.com/spread.asp), which I think were the basis for my misunderstanding. Paragraph 1 seems to define spread as "how large a diamond looks." Paragraph 2 seems to define it as inversely proportional to the depth (the origin of my misunderstanding). The sidebar has yet another definition indicating spread is the diameter itself. This is quite confusing.

This page (possibly and older version of the tutorial?) provides a slightly different view on spread, while still containing a small amount of ambiguity. It does provide more information on how the HCA is calculated, though.

Any comments?

 

[lonebrave]

Oh yeah, much thanks for helping me through this! I am grateful.

 

[JulieN]

The wording was awkward.

Yes, inverse depth is useless.

In HCA, spread is qualitive(I think) In Diam Calc, it is quantitative.

 

[codex57]

Date: 12/11/2006 4:34:08 PM
Author:lonebrave

H&A viewer vs Ideal Scope

Ok, so H&A viewer doesn''t show leakage. I understand how the Ideal Scope works, but not how this works. How is it different in function?

Ideal Scope doesn''t show hearts (I thought I read that somewhere). The redder the better, except the arrows should be grey/black. Pink and white indicate light leakage


Lighting

How do the different types of lighting affect a diamonds appearance (sun/natural, fluorescent, incandescent, etc)?

One of my biggest fears is that I''m been shown something in a ''favorable'' lighting condition at a B&M and it''s masking/enhancing something abnormally.

H&A viewer just shows the hearts and arrows. You flip the stone upside down to see the hearts. I think it has to do with how the light is reflected. The one I used showed the stone in blue, with the hearts in white I think.

Idealscope shows light leakage so you can see the different facets show up in addition to the arrows.

Lighting is very important. When I bought the e-ring, I made sure to see it in flourescent lighting (couldn''t take it outside for natural light cuz I usually went at night and one store was in a highrise. I wanted to see it in lighting that my wife would normally be in. She doesn''t stand under halogen spotlights. The kinds they have in jewelery stores can make a lump of coal sparkle like a star. Make sure to see it in some other light. I usually just asked to see it in their back office. The IS with the light source will tell you if the RB stone is good cut or not, even if you never leave the display area.

 

[lonebrave]

Date: 12/13/2006 5:01:54 PM
Author: codex57
H&A viewer just shows the hearts and arrows. You flip the stone upside down to see the hearts. I think it has to do with how the light is reflected. The one I used showed the stone in blue, with the hearts in white I think.

Idealscope shows light leakage so you can see the different facets show up in addition to the arrows.

Lighting is very important. When I bought the e-ring, I made sure to see it in flourescent lighting (couldn''t take it outside for natural light cuz I usually went at night and one store was in a highrise. I wanted to see it in lighting that my wife would normally be in. She doesn''t stand under halogen spotlights. The kinds they have in jewelery stores can make a lump of coal sparkle like a star. Make sure to see it in some other light. I usually just asked to see it in their back office. The IS with the light source will tell you if the RB stone is good cut or not, even if you never leave the display area.

Thanks for the info! I''ll have to keep an eye out for the type of lighting in the store.