Question about HCA of pricing.

[dave79]

onward I was starting again doing some research of diamond that I did once before about 4 years ago before purchased a diamond wedding ring for my wife. my curiosity found out that some HCA score high diamond doesn't actually high pricing.

for example,
diamond (A).
https://www.bluenile.com/diamond-de...AMONDS&track=viewDiamondDetails&action=newTab

HCA scored 0.6 but actually selling for $6,287

diamond (b)
https://www.bluenile.com/diamond-de...AMONDS&track=viewDiamondDetails&action=newTab

HCA scored 3.7 but actually selling for $7,188

Anyway, this stone diamond (b) cutting proportion is actually the same as the one that i brought for my wife. (and below GIA report was the diamond I owed). so can anyone explain to me HCA effect the pricing or in real life diamond examination will be more important as price to be pricing? also does my wife ring has a bad cut and why 3.7 HCA scored. Thank you.

 

[OoohShiny]

The HCA tool analyses if the crown and pavilion angles work well together.

If they work well, the diamond should perform well.

If they do not work well, the diamond will be shallow and leak light out of the sides (!ow crown + low pavilion angle) or it will be steep (crown)/deep (pavilion) and leak light out of the sides.

The ray-tracing diagram below illustrates this.



You can also see how the shallow diamond is 'spread-y' (large diameter) for its size, but the steep/deep is smaller in diameter. Buying steep/deep means paying for carat weight you cannot see (because the weight is 'hidden' in the pavilion rather than showing a visible diameter increase).

Plus, look where the rays are coming out of the stone (on the right of the stone, because the light is entering from the left hand side) - on the ideal cut stone they are coming out of the stone from the centre to the very edge, which means it has edge-to-edge brightness and looks bigger. The steep/deep does not return light from the edges, meaning it looks smaller in that way also.

 

[dave79]

Thank for your promptly replied. I’m totally understood your point. But, My understanding is HCA score by cutting of their limit proportion to get that high score. So you meant even same cutting size base on GIA diagram but vary from real life will pull down it pricing?

The HCA tool analyses if the crown and pavilion angles work well together.

If they work well, the diamond should perform well.

If they do not work well, the diamond will be shallow and leak light out of the sides (!ow crown + low pavilion angle) or it will be steep (crown)/deep (pavilion) and leak light out of the sides.

The ray-tracing diagram below illustrates this.



You can also see how the shallow diamond is 'spread-y' (large diameter) for its size, but the steep/deep is smaller in diameter. Buying steep/deep means paying for carat weight you cannot see (because the weight is 'hidden' in the pavilion rather than showing a visible diameter increase).

Plus, look where the rays are coming out of the stone (on the right of the stone, because the light is entering from the left hand side) - on the ideal cut stone they are coming out of the stone from the centre to the very edge, which means it has edge-to-edge brightness and looks bigger. The steep/deep does not return light from the edges, meaning it looks smaller in that way also.

 

[bmfang]

A low HCA score does not necessarily translate to a lower price. Colour and clarity play a major part in diamond pricing as well as carat size. There is also the price of diamond rough at the beginning. If that starting base is high, the finished stone will likely be high in price as well.

The 1.06ct stone is discounted significantly over the 1.04ct stone simply due to the fact it has strong fluorescence and the 1.04 stone has none.

For some strange (or stupid) reason, the trade discounts stones that exhibit fluorescent properties.

The reason why your original stone scored so poorly is due to the angle combination not being complementary to each other. For a 35 degree crown angle, the maximum pavilion angle should be 40.8 for it to score under 2 on the HCA. Your original stone was cut with a 41.2 degree pavilion angle (and given it is a GIA graded stone, that angle on the report is an average of the 8 pavilion angles that are then rounded to the nearest 0.2 degree).

 

[dave79]

A low HCA score does not necessarily translate to a lower price. Colour and clarity play a major part in diamond pricing as well as carat size. There is also the price of diamond rough at the beginning. If that starting base is high, the finished stone will likely be high in price as well.

The 1.06ct stone is discounted significantly over the 1.04ct stone simply due to the fact it has strong fluorescence and the 1.04 stone has none.

For some strange (or stupid) reason, the trade discounts stones that exhibit fluorescent properties.

The reason why your original stone scored so poorly is due to the angle combination not being complementary to each other. For a 35 degree crown angle, the maximum pavilion angle should be 40.8 for it to score under 2 on the HCA. Your original stone was cut with a 41.2 degree pavilion angle (and given it is a GIA graded stone, that angle on the report is an average of the 8 pavilion angles that are then rounded to the nearest 0.2 degree).

I heard about strong flouresence will impact diamond sparkle. The reason I’m here doing research again is I’m helping my buddy for his engagement ring. His girlfriend Kind like the ring of my wife (in real life my wife ring very sparkle) but I told her based on my last research I still able to find better one as I told her because I did the research has been 5 to 6 years ago. So onward when I start doing this again I’m getting confuse with the pricing base on HCA will score, also AGA tool and person in store look at the diamond. My wife ring story is I brought it at retail with no knowledge anything about diamond only known 3 excellent. The ring really brilliant and spark at that time, but when went home google found out HCA score low. However I still kept the stone because I trust my eyes and as my wife like it. Now this process start again and I hope to get a better ideal ring for my buddy gf. Somehow budget is between $6500 (as I paid for mine 5-6 years ago) to $7500 same spec or better. By the way, to my country I’m only able to shop at retail not online. That why I’m here gathering info and knowledge before start shopping around. My question is base on my spec on today diamond trade will I able to get ideal cut within my budget and also HCA is really matter if the diamond really sparkle and brilliant in person. Thank you for taking time on comment.

 

[bmfang]

I heard about strong flouresence will impact diamond sparkle. The reason I’m here doing research again is I’m helping my buddy for his engagement ring. His girlfriend Kind like the ring of my wife (in real life my wife ring very sparkle) but I told her based on my last research I still able to find better one as I told her because I did the research has been 5 to 6 years ago. So onward when I start doing this again I’m getting confuse with the pricing base on HCA will score, also AGA tool and person in store look at the diamond. My wife ring story is I brought it at retail with no knowledge anything about diamond only known 3 excellent. The ring really brilliant and spark at that time, but when went home google found out HCA score low. However I still kept the stone because I trust my eyes and as my wife like it. Now this process start again and I hope to get a better ideal ring for my buddy gf. Somehow budget is between $6500 (as I paid for mine 5-6 years ago) to $7500 same spec or better. By the way, to my country I’m only able to shop at retail not online. That why I’m here gathering info and knowledge before start shopping around. My question is base on my spec on today diamond trade will I able to get ideal cut within my budget and also HCA is really matter if the diamond really sparkle and brilliant in person. Thank you for taking time on comment.

Strong fluorescence may (not will) have a negative impact on a diamond. It may also have a neutral or even positive effect on a diamond. My wife’s stone is one which has medium blue fluorescence and if I could have found a strong or very strong blue fluorescence stone that did not have any impact on transparency, brilliance, fire and scintillation at the time, I would have purchased such a stone (thankfully such stones are available at abrían Gavin Diamonds).

A low HCA score does not automatically guarantee that a diamond is worth buying. You can have a heavily included SI2 or I1 stone that has correct proportions, but I still wouldn’t buy such a stone just because it’s HCA score was under 2. The stone could be dull and not eye clean because of those inclusions.

HCA is used to cull your field of diamonds of those with bad proportions so that with what you are left with, you then have a good base to do further research on how a stone performs. Ideally, you would use HCA in conjunction with Idealscope and ASET images to see what stones perform well or not.

What country are you from? I am presuming one which may have import restrictions (including heavy import taxes) on diamonds - both loose and set.

 

[dave79]

Strong fluorescence may (not will) have a negative impact on a diamond. It may also have a neutral or even positive effect on a diamond. My wife’s stone is one which has medium blue fluorescence and if I could have found a strong or very strong blue fluorescence stone that did not have any impact on transparency, brilliance, fire and scintillation at the time, I would have purchased such a stone (thankfully such stones are available at abrían Gavin Diamonds).

A low HCA score does not automatically guarantee that a diamond is worth buying. You can have a heavily included SI2 or I1 stone that has correct proportions, but I still wouldn’t buy such a stone just because it’s HCA score was under 2. The stone could be dull and not eye clean because of those inclusions.

HCA is used to cull your field of diamonds of those with bad proportions so that with what you are left with, you then have a good base to do further research on how a stone performs. Ideally, you would use HCA in conjunction with Idealscope and ASET images to see what stones perform well or not.

What country are you from? I am presuming one which may have import restrictions (including heavy import taxes) on diamonds - both loose and set.

Malaysia. That the reason why is not popular for online purchase combine is so expensive in here. I will start with the same clarity, cut and color first to know the price, then to find out will I able to get a better cut base on that range of price for better HCA score. Very appreciated for all your further explanation "bmfang".

 

[OoohShiny]

If you can get to Singapore, Jann Paul are very focused on excellent cut quality (but may not be as cheap as finding a good GIA XXX from Virtual Inventory and calling it in to your local vendor).

 

[dave79]

If you can get to Singapore, Jann Paul are very focused on excellent cut quality (but may not be as cheap as finding a good GIA XXX from Virtual Inventory and calling it in to your local vendor).

thank you for your recommendation, but somehow unlikely they will willing to travel there for searching. After this 2 days I had been google around and found out my budget within is unlikely to get ideal cut only willing to fork out at least 8k-9k for the same clarity and color. but remember that is the States price, in here more likely will be more 5-10% more at least. Research told me that HCA doesn't like Steep/ deep diamond, but how come GIA still rate it excellent, which HCA always score it between 3.7 - even 5.5 and the price will not cheap and even more expensive compared to other had HCA score between 2.2 - 2.7 same clarity, color, and carat.

 

[sledge]

In all cases, the HCA is meant as a filtering tool. It can help you narrow the selection down to acceptable choices but does not mean it will guarantee a performing stone.

Some methods that will help you:

1. Limit your search to stones with these parameters:

• 54-57 table
• 60-62.4 depth (prefer <62)
• 34-35 crown (maybe 35.5 if paired with 40.6 pavilion)
• 40.6-40.9 pavilion (maybe 41 if paired with a 34 crown)
• 75-80 lower girdle facets, aka LGF (many prefer 75 for fatter arrows and bolder flashes of light return)
• Angles must be complimentary so you want to pair a shallow crown with a steep pavilion or vice versa. The HCA helps check this aspect.

2. Use the HCA tool to further limit as you want a score of 0-2 but a preference of 1-2 as stones 0-1 tend to be better for earrings, pendants, etc. This isn't a hard and fast rule as some stones less than 1 still look good for an e-ring. Also if the stone is extremely well cut and symmetrical you can go above 2 as well but you need to carefully analyze if doing this.

3. With the list narrowed down, ask for help on this forum. We can guide you further.

4. Request idealscope and ASET images to confirm light performance. Request hearts and arrows (H&A) images to confirm symmetry. Many times these images will be unavailable through virtual inventory and/or retail shops. Alternatively you can buy your own scopes and analyze that way. If doing your own scope, an ASET is the most useful and valuable to have IMO.

5. Post the images for review. We can help you analyze. If good, proceed to purchase. If bad, reject and start over. If none available you have to make a decision based on what is available.

6. Order stone and confirm it looks good to your eyes. If not, start over. If it does, yay, you are done and should post pics of the final product for us to ogle over.

 

[bmfang]

thank you for your recommendation, but somehow unlikely they will willing to travel there for searching. After this 2 days I had been google around and found out my budget within is unlikely to get ideal cut only willing to fork out at least 8k-9k for the same clarity and color. but remember that is the States price, in here more likely will be more 5-10% more at least. Research told me that HCA doesn't like Steep/ deep diamond, but how come GIA still rate it excellent, which HCA always score it between 3.7 - even 5.5 and the price will not cheap and even more expensive compared to other had HCA score between 2.2 - 2.7 same clarity, color, and carat.

GIA triple excellent does not automatically mean that a stone is actually well cut. GIA’s excellent cut grade is too wide for us here at Pricescope. Most diamond cutters will cut stones in such a way so that they reach the first angle combination that meets GIA excellent without needing to sacrifice carat weight.

As a result, a lot of 1 carat stones on the market have been cut just to get them above the 1 carat mark with sacrifices in light performance.

Can understand the inability to get to Singapore if they live anywhere else apart from Johor Bahru where it is a quick trip across the Causeway. You can do a day trip like that, but not really if you live further north like Malacca, Seremban, KL, in one of the northern states like Kelantan or Terengganu or across the ocean in Sabah or Sarawak.

Does Poh Kong (that is the only Malaysian jewellery chain that comes to my mind) have any GIA graded diamonds in stock?

As for shipping online, I am pretty sure that vendors like Whiteflash and Brian Gavin Diamonds are able to ship via FedEx International to Malaysia.

E.g. https://www.whiteflash.com/reviews/diamond-engagement-rings-malaysia/

 

[dave79]

In all cases, the HCA is meant as a filtering tool. It can help you narrow the selection down to acceptable choices but does not mean it will guarantee a performing stone.

Some methods that will help you:

1. Limit your search to stones with these parameters:

• 54-57 table
• 60-62.4 depth (prefer <62)
• 34-35 crown (maybe 35.5 if paired with 40.6 pavilion)
• 40.6-40.9 pavilion (maybe 41 if paired with a 34 crown)
• 75-80 lower girdle facets, aka LGF (many prefer 75 for fatter arrows and bolder flashes of light return)
• Angles must be complimentary so you want to pair a shallow crown with a steep pavilion or vice versa. The HCA helps check this aspect.

2. Use the HCA tool to further limit as you want a score of 0-2 but a preference of 1-2 as stones 0-1 tend to be better for earrings, pendants, etc. This isn't a hard and fast rule as some stones less than 1 still look good for an e-ring. Also if the stone is extremely well cut and symmetrical you can go above 2 as well but you need to carefully analyze if doing this.

3. With the list narrowed down, ask for help on this forum. We can guide you further.

4. Request idealscope and ASET images to confirm light performance. Request hearts and arrows (H&A) images to confirm symmetry. Many times these images will be unavailable through virtual inventory and/or retail shops. Alternatively you can buy your own scopes and analyze that way. If doing your own scope, an ASET is the most useful and valuable to have IMO.

5. Post the images for review. We can help you analyze. If good, proceed to purchase. If bad, reject and start over. If none available you have to make a decision based on what is available.

6. Order stone and confirm it looks good to your eyes. If not, start over. If it does, yay, you are done and should post pics of the final product for us to ogle over.

Thank you of your help. I will use your information starting with my survey. Hopefully I will find something within my budget with that spec.

GIA triple excellent does not automatically mean that a stone is actually well cut. GIA’s excellent cut grade is too wide for us here at Pricescope. Most diamond cutters will cut stones in such a way so that they reach the first angle combination that meets GIA excellent without needing to sacrifice carat weight.

As a result, a lot of 1 carat stones on the market have been cut just to get them above the 1 carat mark with sacrifices in light performance.

Can understand the inability to get to Singapore if they live anywhere else apart from Johor Bahru where it is a quick trip across the Causeway. You can do a day trip like that, but not really if you live further north like Malacca, Seremban, KL, in one of the northern states like Kelantan or Terengganu or across the ocean in Sabah or Sarawak.

Does Poh Kong (that is the only Malaysian jewellery chain that comes to my mind) have any GIA graded diamonds in stock?

As for shipping online, I am pretty sure that vendors like Whiteflash and Brian Gavin Diamonds are able to ship via FedEx International to Malaysia.

E.g. https://www.whiteflash.com/reviews/diamond-engagement-rings-malaysia/

Actually now that had pretty much a lot of fancy jewelry store chain from Hong Kong like Luk Fook and Chow Tai Fook. But, I’m believed price will not be cheap of their follow Hong Kong standard. I will survey around first, if my buddy really don’t mind for traveling then I will contact you here. Thank you for your help anyway.