January – June 2022 Volume 28 Number 1 – Gemmological Association of Australia

IN THIS ISSUE

January – June 2022 Volume 28 Number 1

ARTICLES

Figure 1. Hand specimen with one single and two twinned staurolite crystals in a fine white mica schist host rock from Keuvy, Russia. The presentation style of specimen is typical from this location. Photo courtesy of Craig Bosel.

Staurolite and its Role as an Ornamental

Staurolite is an uncommon ornamental mineral and rarely fashioned as a gemstone. For mineral collectors, staurolite is appreciated for its neat cruciform twinned crystals, and cabinet display specimens of staurolite crystals-in-matrix are sought after items for their aesthetic mineralogy. Staurolite is...

Figure 2. Map showing the 255km diameter scar with the John Saul Ruby Mine, Penny Lane, Umba, Kalalani and Merelani gem deposits on its rim-zone. Unlabelled dots represent additional gem occurrences, most of which are hard rock (primary) occurrences although a few are alluvial. The more productive deposits are indicated by larger dots. Part of the rim-zone of the 1800km diameter scar is indicated by the pink band.

Gemstone Deposits of Eastern Kenya and Tanzania Controlled by Ancient Meteorite Impacts and Continental Collision – an Exploration Model

Transparent coloured gemstones in eastern Kenya and Tanzania were formed during a continent-to-continent collision approximately 600 million years (Ma) ago. The collision reactivated deep fractures formed by meteorite impacts during the Late Heavy Bombardment of Moon and Earth, c.4100-3800 Ma,...

Figure 1. The Anastasia Diamond on loan for display at the Natural History Museum, London. The inclusions appear like glitter inside the stone. Photo courtesy of The Trustees of the Natural History Museum, London.

Black Diamonds and Carbonados: A Reflective Overview

Inspired by the loan of a beautiful black diamond to the Natural History Museum, London, and the frequent lack of detailed information about black diamonds in gemmological texts, this article reviews the nature, colour, and origin of black diamonds and...

Figure 8. A ring comprising many small diamonds thought to be of natural origin by its owner, however the exhibition of strong phosphorescence after SWUV illumination signifies artificial origin.

Using Luminescence for Diamond Identification

The use of ultraviolet (UV) light to stimulate light emissions is a common technique used in mineral identification. Geological museums often include a cabinet showcasing colours of fluorescing minerals under a ‘black light’. In gemmology, fluorescence provides a low-cost method...

Chameleon Diamond

There are some diamond types that a gemmologist might read about, but never actually see. One notable example is a ‘Chameleon’ diamond, named as a result of its colour-changing character, switching between a khaki greenish colour to a golden yellow....