ANKERITE FROM SANDHURST, VICTORIA — COOKSET. 63 



ANKERITE from SANDHURST, VICTORIA. 

 By T. CooKSEY, Ph.D., B.Sc, Mineralogist. 



Among the specimens of minerals in the Museum Collection are 

 two, which were obtained from the New Chum line of reef, Sand- 

 hurst, Victoria, and which had been placed among those of the 

 Calcite group. That these were correctly named seemed doubtful, 

 as the powdered mineral effervesced very feebly with dilute hydro- 

 chloric acid in the cold. A qualitative test showed that both iron 

 and magnesia were present in considerable quantity and a complete 

 analysis furnished the following results : — 



100-62 



•3016 gram of material was taken for analysis, which on treat- 

 ing with hydrochloric acid, left -0107 gram of insoluble matter 

 consisting mainly of albite. By subtracting this insoluble portion 

 from the total quantity taken, namely -3016 gram, and calculating 

 the results on the amount dissolved, that is '2909 gram, the per- 

 centage composition of the three carbonates is found to be : — 



CaCOs 50-76 



FeCOs 23-97 



MgCOs 25-93 



Manganese was not present, neither the borax bead test nor the 

 fusion with nitre and caustic potash giving the manganese reaction. 



The specitic gravity of the mineral is 2-994 (uncorr.) and its 

 hardness about 3-5. 



The crystals consist of very flat rhombohedrons with slightly 

 curved faces occasionally striated, and form the lenticular crystals 

 with sharp edges frequently seen in calcite and more especially in 

 siderite. They are, however, externally slightly altered and the 



