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17ct Alexandrite (Cabochon, 18.02×12.01mm, Bluish Green) vs 17ct Topaz (Cabochon, 18.35×12.23mm, Blue)


Quick summary: When looked from above (face-up position), 17ct Topaz (18.35×12.23mm, cabochon cut) appears 4% larger than 17ct Alexandrite (18.02×12.01mm, cabochon cut). See below how they compare side-by-side on a ring and finger.

17ct Alexandrite (cabochon cut)
vs
 17ct Topaz (cabochon cut)
bluish green
 
blue
18.02×12.01 mm 18.35×12.23 mm
actual size
Actual size of 17ct Alexandrite (cabochon cut, 18.02×12.01mm, Bluish Green color)   Actual size of 17ct Topaz (cabochon cut, 18.35×12.23mm, 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 17ct Alexandrite (cabochon cut, 18.02×12.01mm) on a left ring and finger
64 mm
Right finger image
Ring on a right finger
Blue 17ct Topaz (cabochon cut, 18.35×12.23mm) 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
 72% vs 73%
Saved...
Ring diameter: 16.9 mm
USA UK Asia EU1 EU2
Actual sizes of 17ct Alexandrite Cabochon (18.02×12.01mm, Bluish Green) and 17ct Topaz Cabochon (18.35×12.23mm, 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.


17 Ct Alexandrite (Cabochon) 17 Ct Topaz (Cabochon)
18.02×12.01 mm vs 18.35×12.23 mm
177.46 mm²   184.02 mm²
Face-up size outline for 17ct Topaz (18.35×12.23mm, cabochon cut)
Face-up size outline for 17ct Alexandrite (18.02×12.01mm, cabochon cut)
17ct Alexandrite Cabochon (18.02×12.01mm)
17ct Topaz Cabochon (18.35×12.23mm)
Difference: 4% (6.56 mm²)
17ct Topaz (Cabochon, 18.35×12.23mm) has approx. 4% more face-up area than 17ct Alexandrite (Cabochon, 18.02×12.01mm).


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