SSEF News 2012

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SGG, Zentralkurs April 2012, Flüeli-Ranft News from the SSEF Michael S. Krzemnicki Swiss Gemmological Institute SSEF Photos © M.S. Krzemnicki, SSEF, except where indicated otherwise

The range of colours of the last few months...

Indian treasures! IndianIndian treasures treasures! ! © Swiss Gemmological Institute SSEF

1! New Ruby Deposit: Montepuez in Mozambique

Photo: H.A. Hänni!

Both rubies approx. 15 ct!

Photo: H.A. Hänni! Inclusions may resemble those of rubies from Mogok in Burma

Set of exceptional rubies from Mozambique

Rubies from 5 to 10 ct!

2! From the tourist bazar….

Flux-melt synthetic ruby!

Treated orange star sapphire:

Beryllium diffusion (lattice) and titanium diffusion (surface), both induced during high-T heatings !!

3! 100 ct unheated Sapphire from Ceylon

Fancy coloured diamonds

4! Garnet with interesting features

Pyrope-almandine garnet with hollowed bottom part (to lighten colour) and quartz plate on the base.!

Garnet with interesting features

Viewed in transmission: ! ! weak rhombic sector zoning according to dodecahedral crystal shape !!

5! Historic Jewellery

Renaissance Necklace

6! Art nouveau bracelet

Art nouveau necklace with dragonflys

7! Opal from Ethiopia

Dyed opal from Ethiopia

Dyed opal from Wollo, Ethiopia

8! Dyed opal from Ethiopia

700 ct tanzanite

9! Tourmaline and lepidolite (mica) intergrowth from Paraiba, Brazil

mica reference

Demantoid garnet from Russia

10! Emerald crystal 635 ct; Panjeer, Afghanistan

Alexandrite versus Chrysoberyl

Alexandrite is a variety of chrysoberyl, showing a colour change from daylight to incandescent light (tungsten lamp) due to chromium.

The main colour hue has to change to be qualified as alexandrite; e.g. from bluish green to purple.

11! Visible ! colour change!

incandescent! LED light!

nearly no colour shift! This is not Alexandrite !!

This chrysoberyl does not contain chromium (or only very low traces). It shows only a colour change due to a nearly monochromatic bluish white LED light source!

daylight!

Bastnäsite (Nd) from Pakistan with colour change

daylight! incandescent light!

12! Bastnäsite (Nd) from Pakistan with CC

Neodymium (Rare Earth Element) replacing some cerium is responsible for colour change. !

Colour changing zircon from Burma

13! Colour changing zircon from Burma

daylight! 50 ct! incandenscent light!

Colour changing zircon from Burma

unheated!

heating!

heated! daylight!

These zircons are only revealing a colour change after a heat treatment !!

14! Treated orange star sapphire:

NOTES & NEW TECHNIQUES

A HISTORIC TURQUOISE JEWELRY SET CONTAINING FOSSILIZED DENTINE (ODONTOLITE) AND GLASS

Michael S. Krzemnicki, Franz Herzog, and Wei Zhou

3+ • Cu(Al,Fe )6(PO4)4(OH)8 4H2O, has been known since prehistoric times. It has been widely used in A set of six antique brooches, set with diamonds jewelry in the Middle East (Egypt and Persia), the Far and light blue cabochons, was investigated with East (Tibet, Mongolia, and China), and by native North Americans (Ahmed, 1999; Chalker et al., microscopy, Raman analysis, and EDXRF spec- 2004). Yet turquoise was once very fashionable in troscopy. Most of the cabochons proved to be Europe, especially during the 18th and 19th cen- fossilized dentine, also known as odontolite turies (Bennett and Mascetti, 2003), so it is not sur- (mineralogically, fluorapatite). The brooches prising that imitations were used when genuine also contained turquoise and artificial glass. turquoise was not available. The wide range of turquoise imitations includes secondary minerals from copper deposits such as chrysocolla, dyed minerals such as magnesite or howlite, and artificial materials such as glass or sintered products (Arnould Odontolite: heat treated fossilized ivory! and Poirot, 1975; Lind et al., 1983; Fryer, 1983; Kane, he Swiss Gemmological Institute SSEF recent- 1985; Hurwit, 1988; Salanne, 2009). ly received a set of six antique brooches for In this study, we report on a historic turquoise Tidentification (figure 1). These same pieces had substitute—fossilized dentine, also known as odon- already been presented in Bennett and Mascetti tolite, ivory turquoise, bone turquoise, or French (2003, p. 102) as turquoise jewelry. They were set turquoise. Much of this material consists of fos- with numerous small rose-cut diamonds and a few silized mastodon ivory from Miocene-age (13–16 larger old-cut diamonds, but most prominent were a million years old) sedimentary rocks of the Gers number of light blue to greenish blue cabochons that District between the Aquitaine and Languedoc appeared to be turquoise. Visual examination quick- regions of southwestern France (Reiche et al., 2001). ly revealed otherwise. Considering the historic back- The tusks are hosted by alluvial sediments (molasse ground of these brooches, we were interested in alternating with fine sand and clay facies) that accu- examining the blue gems in greater detail to shed mulated in basins during the erosion of the nearby light on early turquoise imitations. Pyrenees Mountains (Crouzel, 1957; Antoine et al., Turquoise, a copper-bearing hydrated alu- 1997). The fossilized dentine consists mainly of fluo- minophosphate with the chemical formula rapatite, Ca5(PO4)3F; since medieval times, local Cistercian monks have used a heating process to turn the material light blue (de La Brosse, 1626; Réaumur, 1715; Fischer, 1819), which they thought See end of article for About the Authors and Acknowledgment. GEMS & GEMOLOGY, Vol. 47, No. 4, pp. 296–301, to be turquoise. These “stones” were originally set http://dx.doi.org/10.5741.GEMS.47.4.296. in medieval religious artifacts, but came into fashion © 2011 Gemological Institute of America in the early to mid-19th century (Brown, 2007),

Treated orange star sapphire:

Rostellite: fossilized jawbone of prehistoric beaked whales) from New Zealand, including two cabochons cut from the material. The greyish-blue sample was subjected to heat treatment (620°C for 6 hours).!

15! Blue apatite

The blue colour is the result of an absorption band by Mn5+, which is replacing P5+ in

ﬂuorapatite Ca5(PO4)3F!

A guide to the worlds major sources of coloured gemstones, diamonds and pearls.! ! for more details see www.gemexplorer.org! also as a free App available in iTunes, !

16! Thank you for your attention

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