I just ran across a post noting an 84.37 carat diamond up for auction at Sotheby''s Geneva, along with a pic and diamond report #. It has an estimated value of $12-$16 million:
You can see a pic here:
http://www.trendhunter.com/trends/84-carat-dazzler-will-be-sold-at-auction
So, off I went to GIA to pull the report:
http://www.gia.edu/reportcheck/
report #: 15692749
weight: 84.37
Report Type: GIA Diamond Grading Report
Date of Issue: January 26, 2007
Round Brilliant
Measurements: 28.93 - 29.20 x 16.76 mm
Carat Weight: 84.37
Color Grade: D
Clarity Grade: FL
Cut Grade: Excellent
Depth: 57.7 %
Table: 62 %
Crown Angle: 33°
Crown Height: 12 %
Pavilion Angle: 41.2°
Pavilion Depth: 44 %
Star length: 55 %
Lower Half: 80 %
Girdle: Thin, Faceted
Culet: None
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
Then, using the tools I know of to rule diamonds out, I pumped the numbers in to the HCA and Dave Atlas'' DIY Old Cut Grading Tool (any other tools out there, folks?):
http://www.gemappraisers.com/oldcutgrade.asp
The Results:
HCA 3 (Very Good - worth buying if the price is right) Hmm, not sure if $15mill qualifies.
Light Return=VG, Fire=VG, Scintillation=Good, Spread=Excellent
AGA 2A (2A grade on table, crown height and pavillion depth, total depth; 1B on crown angle; 1A on girdle thickness)
Clearly cut for size.
I tried finding something similar from the vendors on Pricescope, but I''m having difficulty finding something comparable to act as a reference point. 
So, is it worth buying?
Quash
You can see a pic here:
http://www.trendhunter.com/trends/84-carat-dazzler-will-be-sold-at-auction
So, off I went to GIA to pull the report:
http://www.gia.edu/reportcheck/
report #: 15692749
weight: 84.37
Report Type: GIA Diamond Grading Report
Date of Issue: January 26, 2007
Round Brilliant
Measurements: 28.93 - 29.20 x 16.76 mm
Carat Weight: 84.37
Color Grade: D
Clarity Grade: FL
Cut Grade: Excellent
Depth: 57.7 %
Table: 62 %
Crown Angle: 33°
Crown Height: 12 %
Pavilion Angle: 41.2°
Pavilion Depth: 44 %
Star length: 55 %
Lower Half: 80 %
Girdle: Thin, Faceted
Culet: None
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
Then, using the tools I know of to rule diamonds out, I pumped the numbers in to the HCA and Dave Atlas'' DIY Old Cut Grading Tool (any other tools out there, folks?):
http://www.gemappraisers.com/oldcutgrade.asp
The Results:
HCA 3 (Very Good - worth buying if the price is right) Hmm, not sure if $15mill qualifies.
Light Return=VG, Fire=VG, Scintillation=Good, Spread=Excellent
AGA 2A (2A grade on table, crown height and pavillion depth, total depth; 1B on crown angle; 1A on girdle thickness)
Clearly cut for size.
So, is it worth buying?

Quash