The golden geyser – Robert Logan Jack and the geology of Mount Morgan, Queensland

Abstract

In 1884 the highly respected Queensland Government Geologist, Robert Logan Jack, was sent to inspect and report on a new gold discovery at Mount Morgan in central Queensland. The find was rumoured to be both rich and geologically unique. Jack was bewildered by the form, structure and exceptional richness of the ore that was being quarried in bulk from the summit of Mount Morgan and in response he proposed the radical theory that the deposit represented the outpourings of an extinct gold-bearing thermal spring. The surface ore was in reality the enriched supergene zone of a massive sulphide ore body, a fact that became more and more evident as the deposit was opened up by subsequent mining activity. Jack's theory of a gold spouting geyser, however, had captured the public imagination, and this, as well as factors related to Jack himself and his relationship with the Mount Morgan Gold Mining Company, gave the theory a life well beyond that justified by the growing evidence of the true nature of the deposit.