Volume 23, Number 3, July - September 2007

Current Issue Vol 23 No 3  
  • Ruby suites from New South Wales
  • Lessons from the history of gems
  • Graphitic inclusions in natural brown diamonds
  • Lune River petrified ferns

(Follow this link for abstracts of past issues)

Ruby Suites from New South Wales

Gayle Webb BA, FGGAA, Dip DT, Dip GR
 Mineralogy Section, Geoscience, Australian Museum

ABSTRACT
New South Wales has at least seven alluvial sapphire localities in which pink, red and purple corundums occur with the usual blue, yellow and green corundums, at Barrington Tops, Macquarie River, Cudgegong River, Swan Brook, Bingara, Tumburumba and Yarrowich Valley. At these sites, ruby varies from a minute percentage of the yield of corundum, as in New England, to 50 per cent in parts of Barrington Tops and a reputed 100 per cent at one Yarrowich site. The term ruby is used here to describe all pink, red and purple corundum. 		 Ruby, 0.80 ct, Gloucester Tops
Ruby, 0.80 ct, Gloucester Tops.
Magnification 20 x.
Photograph G. Webb.

Fact or fiction Lessons From the History of Gems

Dr Don Hoover FGA, FGAA (Hon.)

 
ABSTRACT
In this lecture the author discussed the problems posed by the fabrication and misinterpretation of information or data in the past literature in both the sciences and gemmology. Specific examples from the literature were used to illustrate how false information is propagated over the years from publication to publication.		  Pink Topaz parure
Pink Topaz parure illustrated on the Fall 1986 cover of Gems & Gemology.

Graphitic Inclusions in Natural Brown Diamonds

A.S. Bidny, O.V. Kononov, A.G. Veresov, P.V. Ivannikov
Lomonosov Moscow University, Mosco, Russia

ABSTRACT
 The brown colour of natural diamonds is believed to be related to vacancy clusters lying in {111} planes, or graphitic micro-inclusions that are evolutionary products of the former. The existence of graphitic inclusions in natural brown diamonds was confirmed with Transmission Electron Microscopy. In this work natural brown diamonds were studied using high-resolution Scanning Electron Microscopy (SEM) and colour cathodoluminescent scanning electron microscope (CCL-SEM) to obtain more information about the shape, size and other characteristics of graphite inclusions. These were found to be hexagonal lamellar crystals with size up to 2 µm. These graphitic inclusions display re-crystallised surface micro-relief and disposed in corners between sub-individuals' borders. Also graphitic plates of 10 µm and 1-2 µm thickness were found lying parallel to octahedral faces of the diamond.

Lune River Petrified Ferns

Ross E. Jones
Blackmans Bay, Tasmania

ABSTRACT
Complex geological forces associated with the breakup of Gondwanaland preserved elements of mid-Mezozoic plant communities in the Lune River flora. Located in the south-east of Tasmania, the flora includes permineralised plant material from conifers, cycads, ferns and horse tails of the thirteen fern species described, eight are assigned to the genus Osmundcaulis. The remainder represent five different genera.		  Osmundacaulis griggsii. Stem with naturally weathered leaf bases
Osmundacaulis griggsii. Stem with naturally weathered leaf bases and xylem strands in the transverse section. 24mm diameter.