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18ct Alexandrite (Round, 16.04×16.04mm, Bluish Green) vs 18ct Topaz (Round, 16.33×16.33mm, Blue)


Quick summary: When looked from above (face-up position), 18ct Topaz (16.33×16.33mm, round cut) appears 4% larger than 18ct Alexandrite (16.04×16.04mm, round cut). See below how they compare side-by-side on a ring and finger.

18ct Alexandrite (round cut)
vs
 18ct Topaz (round cut)
bluish green
 
blue
16.04×16.04 mm 16.33×16.33 mm
actual size
Actual size of 18ct Alexandrite (round cut, 16.04×16.04mm, Bluish Green color)   Actual size of 18ct Topaz (round cut, 16.33×16.33mm, Blue color)
 
Actual size is set for screen
Ring: Skin tone:
Ring width: 3.0 mm
Left finger image
Ring on left finger
Bluish Green 18ct Alexandrite (round cut, 16.04×16.04mm) on a left ring and finger
64 mm
Right finger image
Ring on a right finger
Blue 18ct Topaz (round cut, 16.33×16.33mm) 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
 95% vs 97%
Saved...
Ring diameter: 16.9 mm
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Actual sizes of 18ct Alexandrite Round (16.04×16.04mm, Bluish Green) and 18ct Topaz Round (16.33×16.33mm, Blue) 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, Alexandrite will face-up smaller than Topaz for a given carat weight, because it has higher specific gravity (3.73 vs. 3.53 - this means it's "heavier" compared to Topaz 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 Alexandrite (Round) 18 Ct Topaz (Round)
16.04×16.04 mm vs 16.33×16.33 mm
202.07 mm²   209.44 mm²
Face-up size outline for 18ct Topaz (16.33×16.33mm, round cut)
Face-up size outline for 18ct Alexandrite (16.04×16.04mm, round cut)
18ct Alexandrite Round (16.04×16.04mm)
18ct Topaz Round (16.33×16.33mm)
Difference: 4% (7.37 mm²)
18ct Topaz (Round, 16.33×16.33mm) has approx. 4% more face-up area than 18ct Alexandrite (Round, 16.04×16.04mm).


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