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18ct Aquamarine (Cabochon, 20.4×13.6mm, Light Blue) vs 18ct Diamond (Cabochon, 18.72×12.48mm, White)


Quick summary: When looked from above (face-up position), 18ct Aquamarine (20.4×13.6mm, cabochon cut) appears 19% larger than 18ct Diamond (18.72×12.48mm, cabochon cut). See below how they compare side-by-side on a ring and finger.

18ct Aquamarine (cabochon cut)
vs
 18ct Diamond (cabochon cut)
light blue
 
white
20.4×13.6 mm 18.72×12.48 mm
actual size
Actual size of 18ct Aquamarine (cabochon cut, 20.4×13.6mm, Light Blue color)   Actual size of 18ct Diamond (cabochon cut, 18.72×12.48mm, White color)
 
Actual size is set for screen
Ring: Skin tone:
Ring width: 3.0 mm
Left finger image
Ring on left finger
Light Blue 18ct Aquamarine (cabochon cut, 20.4×13.6mm) on a left ring and finger
64 mm
Right finger image
Ring on a right finger
White 18ct Diamond (cabochon cut, 18.72×12.48mm) on a right ring and finger
Your settings
Ring
 Gold
Skin tone
 Light
Ring diameter
 16.9 mm
Ring width
 3.0 mm
Finger length
 64 mm
Finger coverage
 81% vs 74%
Saved...
Ring diameter: 16.9 mm
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Actual sizes of 18ct Aquamarine Cabochon (20.4×13.6mm, Light Blue) and 18ct Diamond Cabochon (18.72×12.48mm, White) as they would appear on a ring and finger. Adjust the ring and finger size to get an idea of how these gemstones would look on your finger.

Where to buy?

For certified gemstones, high-end gemstone jewelry, and birthstone jewelry, see Blue Nile

Face-up Size

All things being equal, Diamond will face-up smaller than Aquamarine for a given carat weight, because it has higher specific gravity (3.52 vs. 2.72 - this means it's "heavier" compared to Aquamarine of the same size). Face-up size also depends heavily on the proportions of the cut.

Face-up area is a measure of the size of the gem when viewed from above (as set in a ring). It tells you how big the gem is at the girdle plane.


18 Ct Aquamarine (Cabochon) 18 Ct Diamond (Cabochon)
20.4×13.6 mm vs 18.72×12.48 mm
227.5 mm²   191.57 mm²
Face-up size outline for 18ct Aquamarine (20.4×13.6mm, cabochon cut)
Face-up size outline for 18ct Diamond (18.72×12.48mm, cabochon cut)
18ct Aquamarine Cabochon (20.4×13.6mm)
18ct Diamond Cabochon (18.72×12.48mm)
Difference: 19% (35.93 mm²)
18ct Aquamarine (Cabochon, 20.4×13.6mm) has approx. 19% more face-up area than 18ct Diamond (Cabochon, 18.72×12.48mm).


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