Òafrica semper aliquid noviÓ - ssefthese opals often craze and form cracks due to drying out. they...
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Presentation by
Michael S. Krzemnicki
Swiss Gemmological Institute SSEF
Photos © M.S. Krzemnicki, SSEF,
except where indicated otherwise
News from the SSEF
SGG, Zentralkurs Mai 2010
Seehotel Wilerbad, Wilen
New ruby mines in Northern Mozambique
“Africa semper aliquid novi”Plinius the Elder (23 - 79 ad.) in Naturalis historia
Niassa Montepuez
Ruby from Niassa in Mozambique
© Swiss Gemmological Institute SSEF
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Generally flat crystals
and fragments, often
heavily fractured and
included.
Mozambique Ruby
© Swiss Gemmological Institute SSEF
Host rock is a kyanite- and siderite-
bearing amphibolite.
Mozambique Ruby
Thinsection under crossed polarizers:
amphibole (multicoloured grains), kyanite
(orange-yellow) and iron-bearing
carbonate (pastel-colour with distinct
cleavage). Image size ca. 6 mm.Photo © Dr. Leander Franz, Mineral.-Petrogr. Institut, Universität Basel
© Swiss Gemmological Institute SSEF
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Often heated
Montepuez
© Swiss Gemmological Institute SSEF
Excellent ruby of 8 ct from Montepuez in
Mozambique. This stone is unheated and
exhibits an impressive purity and a well
saturated colour.
However, many stones are heated either
with a borax flux or fissure filled with lead
glass.
Before treatment Heated with borax Lead glass treate
Inclusions:
Rounded crystal inclusions,
rutile needles, twinning planes,
green amphibole.
- Inclusions ± similar to Mogok, Burma
- Trace elements ± similar to Winza
Montepuez Ruby
© Swiss Gemmological Institute SSEF
Photos © H.A. Hänni, SSEF
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Mogok
Rough rubies of 105 and 83 ct
© Swiss Gemmological Institute SSEF
Sapphire of 196 ctfrom Burma
© Swiss Gemmological Institute SSEF
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An outstanding pair of KashmirSapphires (14 ct each)
© Swiss Gemmological Institute SSEF
Bling bling for your most precious stones...
SSEF Photocard
© Swiss Gemmological Institute SSEF
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The longwave UV test...
Engraved emeralds
© Swiss Gemmological Institute SSEF
From the La Pita mine in Colombia,
ca. 10 cm long and 2.5 cm thick.
El-Itoco Emerald, 472 ct
© Swiss Gemmological Institute SSEF
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Aquamarine of approximately 500 ct
© Swiss Gemmological Institute SSEF
© Swiss Gemmological Institute SSEF
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Large carved nephrite plates
© Swiss Gemmological Institute SSEF
Diamond necklace set in white nephrite,
designed by Wallace Chan.
The nephrite is actually “holding” the diamonds.
...but nephrite can also be used in a different way
© Swiss Gemmological Institute SSEF
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Chalcedony
New Chinese medicine...
© Swiss Gemmological Institute SSEF
Patchy colours, high Zr concentration
± columnar structure from the side.
Inamori synthetic opal
© Swiss Gemmological Institute SSEF
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New opal from Welo province in Ethiopia
© Swiss Gemmological Institute SSEF
Brown patchy opal from Shewa province in Ethiopia has broken in the safe!
Ouups !
© Swiss Gemmological Institute SSEF
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These opals often craze and form cracks due to drying out. They often are
treated with a artificial resin (e.g. polyacryl nitrile)
Fissure filled opal
© Swiss Gemmological Institute SSEF
Small cavity filled with colourless artificial resin (including small air bubbles
and reddish pigments) and a thin slice of artificial resin on the conchoidal
surface of a opal crack.
Fissure filled opal
© Swiss Gemmological Institute SSEF
Opal
untreated
Opal varnished
with epoxy resin
Opal
fissure filled
Polyacrylic
fissure filling
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Although claimed to be still “dripping” with liquid natural silica gel, our samples
showed only clear evidence that they had been soaked in an artifical resin!
“Liquid” opal ???
SEM
© Swiss Gemmological Institute SSEF
Pearls...
© Swiss Gemmological Institute SSEF
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A ring with a “pearl” formed by two blisters.
Historic pearl objects
Historic brooch
with bohemian garnets
© Swiss Gemmological Institute SSEF
Non-nacreous pearls...
© Swiss Gemmological Institute SSEF
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This is the shell,
from which we were told,
the “pearl” below originated.
...and their imitations
Dyed fiber glass bead
Natural Quahog pearl
© Swiss Gemmological Institute SSEF
White glass beads
...and their imitations
Natural
non-nacreous pearls
© Swiss Gemmological Institute SSEF
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Visit of the impressive pearl exhibition in Qatar
Bahrain und Qatar 2010
© Swiss Gemmological Institute SSEF, Verdana, 10pt, normal
Small workshop
To cut sapphires
Chanthaburi, Thailand
© Swiss Gemmological Institute SSEF
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Cutting edge in Paris
© Swiss Gemmological Institute SSEF
A visit to Elahera, Pelmadulla and Ratnapura
Sri Lanka
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Sri Lanka
© Swiss Gemmological Institute SSEF
near Ratnapura
© Swiss Gemmological Institute SSEF
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Low temperature heating (<1000 °C), e.g. Mong Hsu rubies and pink sapphires
effect: colour shift, blue colour component is reduced
Ruby treatment Verdana 24pt, bold
© Swiss Gemmological Institute SSEF
Gemstone market in Ratnapura
Thank you for yourattention