Nacre is the iridescent layers which are
produced by the mollusk to coat the nucleus. Looking
through the drill hole of a pearl with a 10x loupe, or
twirling the pearl around to see how transparent the bead
is are ways of evaluating nacre thickness.
- Very thick: 0.5mm
(millimeter) of nacre, approximately 2 years of
cultivation. Can not see any nucleus with unaided
eye
- Thick: .45mm of nacre,
approximately 1 ½ - 2 years of cultivation. Can
not see any nucleus with unaided eye
- Medium: .35mm of nacre,
approximately 1- 1 ½ years of cultivation.
Nucleus not visible with unaided eye
- Thin: .30mm of nacre,
approximately 9 months to 1 year of cultivation.
To the unaided eye the pearls appear to blink
when twirled
- Very thin: .25mm of
nacre, approximately under 9 months cultivation.
To the unaided eye pearls have fisheye look,
nucleus lines are visible
| Nacre Thickness |
Cultivation Time |
Grade |
| Very thick |
2 years |
10 |
| Thick |
1 ½-2 years |
9 |
| Medium |
1- 1 ½ years |
7-8 |
| Thin |
9 months-1 year |
4-6 |
| Very thin |
under 9 months |
1-3 |
|
|
