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am i doing the HCA right??

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gemz

Rough_Rock
Joined
Jun 1, 2002
Messages
5
I wanna put this diamond I'm keen on to the HCA test. But I'm not sure I'm putting the right numbers in! Help!! :-o

It's HRD-certed, 0.76ct, E, vs1 with nil fluorescence and has the following measurements:

5.97-6.03mm x 3.54mm
pointed culet
58% table width
13.5% crown height
43% pavilion depth
medium 3% faceted girdle

Should these be the numbers I input to the HCA?
table % = 58%
crown % = 13.5%
pavilion % = 43%
culet % = 0.45% (the max in the 'pointed' range given in the table below the HCA)

and this is what I'm most concerned with:
is depth % = girdle add crown height add pavilion depth?
or in this case, 13.5% add 43% add 3% = 59.5% ?

If that's not the 'formula' for depth %, is there any way I can calculate the depth % with the info i've already got?
 

lawmax

Brilliant_Rock
Joined
Dec 31, 1999
Messages
1,317
It's more accurate if you use table percentage and crown and pavilion angles. See if the dealer can get a Sarin or OGI report for you so you can have all the angles.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,656
To get the depth % you divide the depth in mm by the diameter.
Adding the % does not work (for a good reasn that you need not worry about).

Lawmax is right - the angle info is better - and from what we have so far we can say this stone has a good likelyhood of being well cut, it is worth chasing :)
 

gemz

Rough_Rock
Joined
Jun 1, 2002
Messages
5
yippee!! thanks so much for the info u guys, esply you, cut nut!! sure feels good to hear that something i really like is 'worth chasing'!
 

gemz

Rough_Rock
Joined
Jun 1, 2002
Messages
5
hey cut nut,

could i clarify something? should i be using the specs i listed earlier on the HCA? correct me if i'm wrong, but i read this posting on diamondtalk that i believe is yours (not too sure on that though) that "HRD is a reliable govt backed Belgian lab. They have slightly different policy in some cases, but this is not to say GIA is right and they are wrong. The way they list cut %'s for crown and pavilion is next to useless for predicting cut quality."

this diamond i was referring to in my earlier posting is certed by HRD....
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,656
43% is rounded and therefore not as accurate.
Also any culet means the P angle is larger than indicated by the depth%. This is bad.

From the total depth however this stone has a good chance of being well cut. Demand a Sarin report and then enter the angles, or buy and ideal-scope and check it for yourself.
 

gemz

Rough_Rock
Joined
Jun 1, 2002
Messages
5
oh i see! thanks so much for clearing that up! really appreciate all your help and advice! :loopy:
 

square

Rough_Rock
Joined
Jul 1, 2002
Messages
20
cut- any chance you'd explain to me why those #'s don't need to add up (crown+girdle+pavil=depth)? i'm curious b/c i just bought a stone yesterday and realized today they don't add up and i am a super-anal worrier!!
here are my sarin stats, i would appreciate it if you'd let me know what you think:
ct. 1.04, DVS1
diam. 6.58mm
depth 3.96mm, 60.2%
crown 34.7', 14.8%
pavil 40.6', 42.5%
table 3.77mm, 57%
culet 0.9%
girdle 0.7thin - 1.4medium, 1.1%

THANKS IN ADVANCE!
S.
 
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