Volume 24, Number 7, July - September 2011

   
  • Serpentine crystal with purple-red transmission
  • High quality synthetic yellow orange diamond emerges in China
  • Gem-quality green and blue tourmaline from a Coolgardie pegmatite, Western Australia
  • Less frequently encountered gemstones - Painite
Front cover image:
Pin fire tourmaline from  Coolgardie pegmatite, Western Australia. Photo by F. Payette

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Serpentine crystal with purple-red transmission

Gagan Choudhary

 

ABSTRACT
 One dark bluish green serpentine specimen weighing approximately 19.52 grams was encountered at the Gem Testing Laboratory Jaipur, India. The specimen was unusual for its crystal form and purple-red transmission in strong light. Serpentine, which is usually found as massive boulders, was seen here as a crystal with bladed habit and displayed fine striations on the surface due to cleavages. Further, this crystal also displayed a strong purple-red transmission in strong light; the effect was mistaken for colour-change effect and the sample was misrepresented as alexandrite.

 

Serpentine with purple red transmission

The serpentine specimen appeared purple-red when observed in strong transmitted light; an unusual phenomenon for serpentine. This effect is mistaken for a colour-change effect and such specimens are misrepresented as alexandrite.

High quality synthetic yellow orange diamond emerges in China

Song Zhonghua, Lu Taijin, Shen Meidong, Su Jun and Shang Jingjing

China synthetic diamond
The 1.57 ct orange yellow synthetic diamond. Photomicrograph by Song Zhonghua. 		ABSTRACT
In recent years, the commercial availability of gem-quality synthetic yellow diamonds has caused great concern in the gem and jewellery industry. To accurately identify synthetic yellow diamonds grown by HPHT techniques, the gemmological characteristics of gem-quality synthetic diamonds available in China are given and discussed. The DiamondViewTM imaging system, photoluminescence (PL) spectroscopy, as well as microscopy, are the most useful techniques for an effective identification. The presence of peaks at 727 nm, 747 nm, and 753 nm (due to nickel) in the PL spectrum provides evidence of the synthetic origin.

Gem-quality green and blue tourmaline from a Coolgardie pegmatite, Western Australia

Francine Payette and Dr Leonhard Klemm

ABSTRACT
In Western Australia, the Coolgardie pegmatite field is best known for its world-class specimens of ferrocolumbite that have been mined for many decades from the Giles beryl-columbite pegmatite at Spargoville. Recently, gemmy green and blue tourmalines have been found in a pegmatite south of the beryl-columbite pegmatite.

The tourmalines were analysed using standard gemmological instruments, and their chemical composition was determined by LA-ICP-MS. The gemmological and spectroscopic properties of tourmaline from this locality are consistent with properties of tourmaline from other localities worldwide. The LA-ICP-MS analyses indicate that the tourmalines are predominantly elbaite with subordinate foitite and some minor olenite and schorl components.

Coolgardie tourmalines
A representative selection of Coolgardie tourmaline colours. Length of blue rectangular step cut specimen at right, 10.5 mm. Photo by F. Payette. .

Less frequently encountered gemstones - Painite

Rod Brightman

ABSTRACT
Mention painite to most gemmologists prior to 2002 and they would have immediately thought of the world’s rarest gemstone. Originally described by Claringbull et al. (1957), and named after the famous mineralogist and gemmologist Arthur Charles Davy Pain who first identified it as samples of an unknown mineral in 1952, only three rough crystal specimens were known until a new occurrence was located in 2002. Between 2001 and 2005 extensive exploration in the Mogok area of northern Myanmar (Burma), resulted in several thousand specimens being located, although most of these were non-gemmy. Most are fragments with well-formed crystals being quite rare and of these, relatively few have been faceted into transparent gemstones. Gemmy faceted specimens would still have to be regarded as an extremely rare collector gemstone and up until 2004 there were only two known faceted specimens.
Polysynthetic twin lamellae viewed through the crown facets of the painite (0.79 ct). Photo by F. Payette.