diamond weight estimation

[Eightball]

If the specific gravity of a diamond x 0.0018 = 3.52 x 0.0018 = 0.006336

Why do I see 0.0061 also used as the constant ?

 

[Richard Sherwood]

The .0018 figure is usually used (along with specific gravity) as the colored stone formula for figuring the weight of rounds, while the .0061 figure is used as the diamond formula factor for figuring round weight.

I''m thinking that the larger number is used for colored stones because they are usually not as streamlined and precisely symmetrical as diamonds, and carry a little more weight because of it.

Both diamonds and colored stones will often have additional girdle width factoring, while colored stones will often have additional "bulge" factoring as well.

 

[oldminer]

Rich is right, as usual..... Girdle thickness of diamonds is generaly less than with colored gems. Colored gem pavilions generally are made with a bulge and diamonds are not.... If you ever see a "diamond cut" sapphire you will note how it looks quite different than most regular cut sapphires. It also will weigh less than the colored gem formula would indicate,,,,,because it is cut like a diamond and not cut like a sapphire generally is cut.

 

[Eightball]

Thanks. That makes sense. I''ll stick with 0.0061.