112 RECORDS OF THE AUSTRALIAN MUSEUM. 



Mr. Gibb Maitland, Assistant Government Geologist for Queens- 

 land, writes me that this and similar specimens were found in 

 Number 1 1 Floor, Freehold South Stopes, thirty-eight feet below 

 the surface of the ground. They occur in a matrix of oxide of 

 iron, the latter forming a dyke, eighteen feet in width, dipping to 

 the north-east, and consist of nodules of all conceivable shapes and 

 sizes, surrounded by iridescent oxide of iron, manganese, and 

 other auriferous clayey matter. 



Mr. Jack expressed the opinion that their origin was not organic, 

 which was subsequently confirmed by the Curator of the Australian 

 Museum. A superficial examination of the specimen in question 

 supported this view, and determined it to be a concretion of a 

 basic sulphate of iron containing alkalies. On the strength of this 

 result, Mr. W. R. Hall presented to the Trustees of this Museum 

 the specimen already received. It seemed to me that a more exact 

 determination of the nature of the body would be of interest. 



Properties. — To the naked eye the specimen appears a compact 

 mass of a dull brown colour weathered slightly on the outside to a 

 yellow powder. The powdered substance itself has a yellow colour, 

 and under the microscope is seen to consist of minute crystals. It 

 is but very slightly soluble in water, but completely soluble on 

 boiling for a short time with hydrochloric acid. Heating in a tube 

 causes a liberation of acid water and the substance on cooling turns 

 red. Before the blowpipe it turns black, becoming highly magnetic, 

 and slightly fuses on the edges. Its specific gravity is 3-107. 



An analysis gave the following percentage composition — 



100-71 



No water was given ofFby heating the powdered substance to 1 75° C 

 for two hours. The above percentage for water was obtained by 

 heating a weighed quantity to dull redness for a short time, 

 noting the loss of weight, and then estimating the quantity of 80 3 

 left in the residue. From these numbers and the known total 

 of SO 3 in the substance the amount of water was calculated. 



By extracting twice with boiling water, 0-8% was dissolved, 

 which contained a trace of chloride, probably salt. 



The specific gravity and the analysis, with the exception of the 

 proportion of potash to soda, agree very closely with those given 

 by Dana in "A System of INIineralogy." p. 975, for Jarosite, but 

 the insoluI)ility in water of the Mount Morgan mineral seems to 

 show that tlie two bodies cannot be identical. The latter body 

 is, without doubt, derived from the decomposition of pyrites. 



January, 1896. 



