Date/Time
Date(s) - 14/07/2021
8:00 pm

Categories No Categories

Speaker:

Murray Thompson, Desert Fire Designs

Topic/presentation:

GREEN ‘N GOLD

Date/Time:

Wednesday 14 July 2021, 8pm

(venue opens at 7pm for socialising)

Venue:

WA Lapidary and Rock Hunting Club Inc.
31 Gladstone Road, Rivervale

Abstract

The Marshall Pool area, located about 85 km north of Leonora on the Goldfields Highway towards Leinster, is a particularly rich source of chrysoprase, and it has been described as a discrete part of the highly mineralised Greenstone Belt. I visited Marshall Pool in Aug/Sept 2019, and I will concentrate on these newer workings in my presentation. The gem rough material I inspected and have since worked from the Marshall Pool deposit presents primarily in nodular form, with sizes ranging from less than 100 grams to boulders in excess of 350 kilograms. Buying parcels of translucent, gem grade, chrysoprase either in the field or the workshop is fraught with issues. These will be discussed together with the solutions we have worked through to produce world class quality finished gems.

Beta Hunt is an underground nickel mine located 2 km southeast of Kambalda and 60 km south of Kalgoorlie in Western Australia. The mine is located on the northern edge of Lake Lefroy a medium size salt lake lying within the Lefroy Paleodrainage. Although patches of gold have been found at Beta Hunt since nickel mining began, it was not until 1978–79, when underground development reached the deeper levels of A Zone and of D Zone that the presence of a major gold mineralised system was confirmed in the footwall basalt. High temperature, high pressure, hypersaline, silica-rich, migrating ore fluids cause hydraulic fracturing and they also cause wall-rock alteration — these features and the effect they had on the already mineralised host rock will be explored in the talk. In September 2018, the RNC mining company intersected the single largest occurrence of this style of mineralisation, known as the Father’s Day Vein discovery. An estimated 25 000 oz of gold was recovered from a single development drive cut on Level 15 in the A Zone.

Within and between these geographically disparate mineral sites lies a common denominator — this too will be discussed and the effect it had on these deposits.

Biography – Murray Thompson BSc CF FGAA

Murray has been working in gemmology for over 48 years, starting with a city-based jeweller in Adelaide, where he studied gemmology, valuing and store management. He progressed to faceting Australian emeralds in Kalgoorlie and prospecting for gold in WA before returning to Adelaide, where he opened a gem cutting business. In 1987 Murray won a Churchill Fellowship for international gem fashioning and display, which allowed him to visit gem cutters, jewellery stores, museums and gemmological studios across the world.

After more than a decade of gem cutting, Murray moved to Perth where he studied geology at Curtin University and the Kalgoorlie School of Mines, then worked as a geologist. He earned his stripes first as a pit geologist at the Tarmoola gold mine north of Leonora then at the Mt Keith open cut nickel mine as senior resource geologist, before moving further afield into copper/gold at the DeGrussa mine north of Meekatharra.

After retiring from exploration, Murray resumed his gem fashioning business as he believes that not enough has been done in the past to bring out the very best that Western Australian gem rough material has to offer. He is working towards amending that via is workshop and business Desert Fire Designs.