Br w F. I'i/ri i:iM). 67 



development in stellar and cruciform triplet 

 crystals. 



It is noticeable that, while the variety under review 

 is invariably associated with the chromateo£lead,the 

 common type is rarely, if ever, obtained in the 

 vicinity. It is always opaque, with a shining lustre, 

 but not adamantine. The colour is canary yellow, 

 wiith an occasional tinge of red where the crystal has 

 impinged upon the chroraate. The tint does not 

 vary to any serious extent, although paler examples 

 are occasionally met with. It is a most attractive 

 mineral, and soon arrests attention. Its most con- 

 stant feature is its crysftallisation in flatish frondoae 

 and spear-headed groups, twinned by repeated angles 

 across different faces of the prism (110). The 

 striated faces of the twinned gToups are the brachy- 

 prisms Oil and 013; these are commonly deeply 

 grooved, affording a most interesting leaf-life and 

 unfamiliar appearance. 



This variety is perfectly distinct, both as regards colour 

 and habit of crystallisation. Moreover, intermediate 

 variations between it and normal type have not been 

 met with. It is undoubtedly one of our most attrac- 

 tive and typical minerals. Under the blowpipe gives 

 reactions for chromic acid. 



12 Dolomite {Carhonate of inagnesiuni and calcium.) 



A somewhat unusual occurrence, in the form of small 

 attached, doubly-curved or saddle-shaped crystals, 

 which are opaque and white. Magnet Silver Mine, 

 Magnet. 



13 DioPSiDE (J\Ietasilicate of calciniu, iron, and uianganese.) 



This almost white variety of pyroxene occurs, both 

 massive and crystallised, at the Tenth Legion Mine, 

 Comstock District. Analysis : — 



Si O2 = 52-1 



AI2 O3 = 3-0 



Mg O = 15-0 



Aa O = 27-7 



Fe = 2-3 



100-1 



Specific gravity 3.23; hardness, about 6. (G. Waller: 

 Report on the iron and zinc-lead ore deposits of the 

 Comstock District, 1st February, 1903.) 



