carat vs. color  length*  width*

(or examine a single gem)
* size in mm (optional)

1 Ct Tanzanite (Round)


1 Ct Alexandrite (Round)

light green
6.37×6.37 mm 6.14×6.14 mm
actual size
Actual size of 1ct Tanzanite   Actual size of 1ct Alexandrite
Actual size is set for screen Change
Ring: Skin tone:
Ring width: 3.0 mm
Left finger image
Ring on left finger
Blue 1ct Tanzanite on a ring
64 mm
Right finger image
Ring on a right finger
Light Green  1ct Alexandrite on a ring
Your settings
Skin tone
Ring diameter
16.9 mm
Ring width
3.0 mm
Finger length
64 mm
Ring diameter: 16.9 mm
Actual sizes of 1ct Tanzanite Round (6.37×6.37mm, Blue) and 1ct Alexandrite Round (6.14×6.14mm, Light Green ) 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 Tanzanite or Alexandrite check what Amazon has to offer. You'll usually find quite a selection from many different vendors. Worth a check. For other high quality gemstones (Rubies, Saphhires, Emeralds) and especially Diamonds, I highly recommend JamesAllen.

Face-up Size

All things being equal, Alexandrite will face-up smaller than Tanzanite for a given carat weight, because it has higher specific gravity (3.7 vs. 3.3 - this means it's "heavier" compared to Tanzanite 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.

1 Ct Tanzanite (Round) 1 Ct Alexandrite (Round)
6.37×6.37 mm vs 6.14×6.14 mm
31.87 mm²   29.61 mm²
Face-up size outline
Face-up size outline
1ct Tanzanite Round (6.37×6.37mm)
1ct Alexandrite Round (6.14×6.14mm)
Difference: 8% (2.26 mm²)
1ct Tanzanite Round (6.37×6.37mm) has approx. 8% more face-up area than 1ct Alexandrite Round (6.14×6.14mm).

Popular comparisons:

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Actual size is currently adjusted to screen.

If your screen (phone, tablet, or monitor) is not in diagonal, then the actual size of a gem, ring and finger will not be shown correctly.