By Tony Forsyth

After Robert L. Jack, the most influential person in Queensland mineralogy was probably Benjamin Dunstan. Working for the Geological Survey of Queensland since before the turn of the century, Dunstan rose to head the Survey for over two decades. He is credited with publishing many important reports, with a keen eye for the unusual and a genuine love of minerals. He was also a fine draftsman, and his illustrations contained in the reports are particularly detailed.

His major work the ‘Queensland Mineral Index’ published in 1913, is still a standard text today, and is not likely to be matched, listing over 18,000 entries of mineral occurences around the state. Here are two illustrated excerpts from reports written in 1904 and 1905, obtained from the the Department of Minerals and Energy Library.

Dee River Nugget
Last century much debate occurred amongst the mining fraternity on the origin of gold nuggets. Were they deposited and built up to a lump from the fine grounds of gold in the streams, did they precipitate from solutions or did they merely erode from larger gold specimens and were waterworn?

Benjamin Dunstan seemed to have an answer when a large nugget was discovered in the Dee River not far from Mount Morgan near Rockhampton in Central Queensland.

"...the evidence on this point showed conclusively that the gold had formed in association with quartz. The 85½ oz. nugget, on examination besides showing a frosted surface, was found to be penetrated by a number of six-sided holes. On closer inspection, after the specimen was cleaned, these holes proved to be the casts of quartz crystals, in which all the well known peculiarities of crystallisation of that mineral were reproduced, showing undoubtedly the gold to have been deposited in a vugh or cavity containing a cluster of quartz crystals. The following rough sketch will show how the gold occurred, and from it the conclusion will be drawn that the size and shape of the gold nuggets were very different when enclosed in the cavity of quartz crystals from what they were when found in the alluvial wash, after being worn into their present form by attrition".

Extract from the Geological Survey of Queensland Publication No. 190, Records No. 1, By B. Dunstan (Acting Government Geologist) 1904

Selected Mineral Notes

Calcite Crystals with Pyrites
Inclusions, at Golden Gate, Croydon
In the block shaft being sunk at Roger’s Extended Mine, on the Golden Gate line of reef at Croydon, a quartz reef has changed into calcite, in the cavities of which calcite crystals have been formed.

"Figure 2, Plate 5, shows the general appearance of the crystals as they appear in groups, with the lines of pyrites inclusions passing through them. Figure 1, on the same plate, illustrates the character of the twinning, the pyrites dust inclusions on the terminal faces, and the median line of microscopic crystals of pyrites traversing the group of calcite crystals at right angles with the principal axis".

Figure 1.

Figure 2.

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