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32th IGC Conference, July 2011

Interlaken

Tokki Pearls:

Additional cultured pearls formed during pearl cultivation: External and internal structures

M.S. Krzemnicki1, Müller2, H.A. Hänni3, H-P. Gut4, M. Düggelin5

1Swiss Gemmological Institute SSEF, Basel, Switzerland, 2Hinata Trading Ltd., Kobe, 3GemExpert, Switzerland 4Gloor Instruments, Uster, Switzerland 5Centre for Microscopy, University Basel, Switzerland

“Tokki” is a Japanese term Tokki pearl to describe small „bumps“ (or additional cultured pearls) attached to a larger beaded .

© Swiss Gemmological Institute SSEF

1 Tokki pearl

We can distinguish three types of Tokki pearls:

Type A Type B Type C with an irregular cavity with an irregular cavity with a small additional connected to the of („moustache“) cultured pearl the larger cultured pearl surrounded by

© Swiss Gemmological Institute SSEF

Tokki pearl type A

X-ray computed microtomography (coronal sections): Tokki mxt 14b

© Swiss Gemmological Institute SSEF

2 Models of Tokki pearl formation

Tokki Type A: First generation

epithel cavity nacre bead

grafting epithelium “bulging“ nacre deposition Tokki pearl type A

© Swiss Gemmological Institute SSEF

Models of Tokki pearl formation

Tokki Type A: Second generation

bead for 2nd beaded CP generation CP cavity due to incision wound

incision

Tokki pearl first harvest nacre deposition type A

© Swiss Gemmological Institute SSEF

3 Tokki pearl type B

Tokki No. 3

SEM micrograph

© Swiss Gemmological Institute SSEF

Tokki pearl type B

organic rich matter

nacre carbonate aggregates („globuli“)

4 nacre Tokki 24 Calcium organic rich matter carbonate aggregate

organic rich matter due to a second hemorrhage into the pearl sac

nacre

Tokki pearl type B

Transaxial microtomography sections Coronal microtomography sections

Tokki No. 4 Tokki No. 7

© Swiss Gemmological Institute SSEF

5 Models of Tokki pearl formation

Tokki Type B: First generation

Small „folding“ „moustache“ Two tissues tissue become one piece

formation of docking of independent beadless CP tissue „wrapping“ Tokki pearl grafting beadless CP on beaded CP and nacre cover type B

© Swiss Gemmological Institute SSEF

Tokki pearl type C

© Swiss Gemmological Institute SSEF

6 Tokki pearl type C

nacre Tokki No. 19

Loose structures (rich in organic matter) Large drying fissures

Whitish layered CaCO3 „globuli“ interlayed in conchioline

© www.homoeopathie-allenstein.de

7 organic-rich layer

nacre

Tokki No. 13b

Large core with fine-porous and dense columnar intergrowth of

CaCO3

Tokki pearl type C

Tokki No. 10 transaxial sections

© Swiss Gemmological Institute SSEF

8 Tokki pearl type C

Tokki No. 15, coronal sections © Swiss Gemmological Institute SSEF

drying fissures

latest nacre layer

Tokki No. 22 loose nacre layers

9 Soap bubbles....

Models of Tokki pearl formation

First generation Tokki Type C:

CaCO conchioline-rich tiny 3 „spot“ layers Two tissues tissue become one piece

formation of docking of independent additional CP tissue „wrapping“ Tokki pearl grafting additional CP on beaded CP and nacre cover type C

© Swiss Gemmological Institute SSEF

10 Pertinence for pearl testing

Additional cultured pearl formation: First generation

CaCO Additional tiny 3 „spot“ cultured pearl tissue piece

formation of independent additional CP grafting additional CP remains loose

© Swiss Gemmological Institute SSEF

Pertinence for pearl testing

Detection of additional cultured pearls !

mxt61_20

© Swiss Gemmological Institute SSEF

11 Pertinence for pearl testing

Natural or cultured pearls ?

Photo & Radiography © GPTL

Pertinence for pearl testing

Loose ring structures (conchioline-rich) whitish „globuli“

former „docking“ feature of Tokki pearl to larger beaded CP pearl Photo & Radiography © GPTL Bahrain

12 Pertinence for pearl testing

Additional cultured pearls:

whitish globuli

mxt61_20

White CaCO3 central spot

© PhotoSwiss &Gemmological Radiography Institute© GPTL BahrainSSEF

Conclusions Tokki pearls are a by-product of pearl cultivation

We distinguish three types of tokki pearls (cultured pearls) depending on their internal structures.

Tokki pearls may fall from the larger cultured pearl during harvesting or even not attach to the cultured pearl at all; thus be present as loose additional cultured pearl!

Tokki pearls (and additional cultured pearls) generally are characterised by loose ring structures, distinct drying fissures, a central core surrounded by organic-rich layers, and often irregularly distributed small calcium carbonate spheres („globuli“)

Using radiography and microtomography, Tokki pearls and additional cultured pearls can be detected.

© Swiss Gemmological Institute SSEF

13 Thank you for your attention

Acknowledgements: - Andy Müller for the donation of many cultured pearl samples - Sam Buchanan for comments and discussions - Dr. Franz Herzog and Piotr Halicki for many pearl radiographies - Ali Safar and Abeer Al Alawi from the Bahrain Pearl and Testing Laboratory for radiographies and fruitful discussions

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