RB Dimensions

[rocksolid]

Are RB measurements based on the diameter of the stone both vertically and horizontally (right down the middle), or is it based on something else? How do you measure the area of the stone?

I have searched the forum for a clear answer, but can''t seem to find one. Thanks!

 

[kcoursolle]

Yes, RB are measured by the diameter of the stone. They measure the smallest and largest diameters and report those two. To get an idea of size comparison, you can get the area of the top (like a circle) by using the equation pie r squared. R is the radius which is half of the diameter. I''m not sure of a way to get the area of the entire stone...it would have to be a very complicated equation to include the pavillion and crown.

 

[JulieN]

the minimum diameter, maximum diameter, and depth are the dimensions.

the average diameter is what the rest of the percentages are based on.

 

[oldmancoyote]

What do you want to use the area of the stone for? (We may be able to get an easier proxy for that than the precise formula, which is long if not complicated)

 

[rocksolid]

I saw on a website that the measurements are based on the side measurements and not the middle (not sure if that makes sense), so that got me really confused. for example, the measurement would be based on the length of the line drawn through this smiley''s eyes:

if RB''s are measured by diameter, then they need a lot more diameter to make up for the "corners" that are missing when compared to say, a cushion, right?

thanks for your responses- i''m just curious!

 

[JulieN]

Say you wanted to measure the diameter of a circle.

1. You could take a ruler and put the edge through the middle.

2. You could use a caliper ruler, which is edge-to-edge.

I think of cushions as missing "bulges" rather than a round missing "corners." But it is not important.

 

[oldmancoyote]

Uh? Where on Earth did they write anything like that? These people need to be taken and hung by what sticks out of their diameters.

Sorry - diameter has a precise geometrical meaning. It''s a straight line that goes through the centre of the circle and joins two opposite points on the circumference. If it''s not going through the centre, it''s not the diameter, it''s a cord. And (assuming a round brilliant is truly circular) rounds are measured by their diameter.

Since they are not perfectly circular, labs measure the diamond at different points along the girdle, and report minimum and maximum measurement - but they are all diameters (or as close as they can get) in the geometrical sense of the word.

 

[rocksolid]

Date: 1/9/2009 6:22:04 PM
Author: oldmancoyote
Uh? Where on Earth did they write anything like that? These people need to be taken and hung by what sticks out of their diameters.


Sorry - diameter has a precise geometrical meaning. It''s a straight line that goes through the centre of the circle and joins two opposite points on the circumference. If it''s not going through the centre, it''s not the diameter, it''s a cord. And (assuming a round brilliant is truly circular) rounds are measured by their diameter.


Since they are not perfectly circular, labs measure the diamond at different points along the girdle, and report minimum and maximum measurement - but they are all diameters (or as close as they can get) in the geometrical sense of the word.

this is where i saw the measurements...it''s a little bit misleading, right?

http://www.bluenile.com/round-diamond-1-carat-or-less-signature-ideal-cut-h-color-si1-clarity_LD01193352?__fun_frm=i&filter_id=0

click on the picture that shows the dimensions.

 

[rocksolid]

Date: 1/9/2009 6:16:56 PM
Author: JulieN
Say you wanted to measure the diameter of a circle.


1. You could take a ruler and put the edge through the middle.


2. You could use a caliper ruler, which is edge-to-edge.


I think of cushions as missing ''bulges'' rather than a round missing ''corners.'' But it is not important.

thanks julie. that makes sense.