NOTES FROM THE AUSTRALIAN MUSEUM. 



ON SOME REMARKABLE CRYSTALS OF SIDERITE. 



By F. Ratte, 



" Ing. des Arts et Manuf." (Paris.) 



(Plate LVI.) 



The object of this note is to record the occurrence of a group of 

 crystals of siderite or carbonate of iron, arranged in so perfect 

 and regular a manner that the case must be considered to be very 

 i-are. 



It is well-known that this mineral is frequently found in 

 lenticular, curved, distorted or even saddle-shaped crystals. These 

 irregularities arise from the modification termed " equiaxe " when 

 the solid angles appear rounded and the faces and the edges 

 curved. One of these crystals isolated, is shown at the foot of 

 fig. 1 (cZ), among some lenticular crystals of calcite, and others 

 exist on the speciuien which are not shown on the figure. 



The group alluded to is formed of three principal crystals, each 

 presenting the shape of a complete saddle, only about 100° or so 

 being wanting to make it cup-shaped. These three crystals are 

 I'egularly grouped so that their axes of symmetry are at about 

 120" respectively. A few lenticular and curved crystals spring 

 from the centre of the group. 



This remarkable group is attached to a perfect crystal of quartz 

 terminating in two six-sided pyramids which has itself been 

 enveloped by a larger crystal of quartz. This specimen has been 

 secured for the Australian Museum, and is from the auriferous 

 quartz reefs of Sandhurst, Victoria. 



