24 



RECdKliS OK TUK AUSTI.'AI.IAN MllfrEDM. 



face at tlie back of the drawing is i-ougli ami iiregalar, and evidently the 

 crystals were attached to the matrix by it; apparently the crystals were 

 implanted on quartz. Tlie base is usually juesent as a wavy face giving 

 pool' reflections. The faces of (( (100) are smooth, with the exception of 

 the face of attachment, but )it. (110) shows conchoidal markings and small 

 etch pits. 



Ko!ins and Antfles : 



I'ilbara, Western Austj-alia. 



(PI. vii., lig. o.) 



This tine crystal, which is one of two kindly lent by iir. W. T. 

 VVatkin Biown, is about 1 cm. in diametei-; it is a doublet on the usual 

 law and, since rei-ntrant angles are practically absent, the twin looks at 

 Hrst like a simple crystal of pyramidal habit with a large number of 

 faces. The planes are mostly well adapted (o goniomet ric measurement, 

 and the measured and calculateil angles aie in good agreement. 



