July – December 2023 Volume 28 Number 4 – Gemmological Association of Australia

IN THIS ISSUE

July – December 2023 Volume 28 Number 4

ARTICLES

Figure 11. A polished face of precious boulder opal from the Arch Mine. (Photo A. Kent).

Queensland Precious Opal Deposits and Associated Critical Mineral Enrichment within Silicified Palaeochannels

Queensland boulder opal host rocks were investigated and geochemical markers identified that are indicative of the presence of precious opal. Artesian groundwater migrating and accumulating in sandstone palaeochannels was subject to changes in pH, leading to opalisation within structural and...

Figure 1. The necklace showing the range of collet-set gemstones interspersed with gold chain.

A Story in a Gemstone Necklace

The multi gemstone necklace (Figure 1) featured here contains no unique or rare gemstones, nor is it especially valuable. The identification project described is, however, interesting for the many practical results and observations that bring together evidence from methods of...

Figure 1. A sample of colours of commercially available synthetic moissanite.

Surface-Coated Synthetic Moissanite Now Widely Available

The Victorian Division of the GAA has just purchased a parcel of interesting, surface-coated moissanites to add to the gemmological collection. These brightly coloured stones come with certificates and are laser inscribed on the girdle. While the process of identifying...

Figure 4. A collection of eight ‘eye agates’ showing diversity of colour and form (largest, on left, 126g; 56x47x39mm).

Unusual Chalcedony-Agate Pebbles from the Gobi Desert

I have been a rock collector for as long as I can remember, from the first time I visited a stony English beach as a child and felt the need to pick up the most interesting pebbles and put them...

Figure 2. Agate Creek thunder eggs with star-shaped cavity. Left: cavity filled with layers of red and white cryptocrystalline quartz. Right: cavity infilled with colourless crystal quartz.

The Agate Man – Sir Paul Howard

Agate Creek is a world-class Australian fossicking area located in remote northern Queensland. Its beautiful agates and thunder eggs are sought by collectors worldwide, each one being unique. This article honours the lifelong work of Paul Howard on the Agate...