BOLEITE, NANTOKITE, KERARGYRITE AND CUPRITE. 95 



dried at 100° C, at which temperature it did not change in weight, 

 then mixed with sodium carbonate, previously dried at a red heat, 

 and fused in a hard glass tube through which a current of dry air 

 was drawn ; the water was arrested and weighed in a tube of 

 pumice stone moistened with pure sulphuric acid. 



The amount of water is rather higher than the percentage 

 calculated by Messrs. Armstrong and Carmichael, this may be due 

 to the sodium carbonate not having arrested all the chlorine and 

 a little of the oxide of lead may have been carried forward, 

 although the process was conducted as slowly and carefully as 

 possible. I had, unfortunately, so little of the mineral that I was 

 unable to perform any check experiments. 



Mr. McKay states that the specimen was thought, by the finder, 

 to be azurite, and that he (Mr. McKay), did not receive it for some 

 days, when there was no possible chance of getting further speci- 

 mens. This is much to be regretted since the mineral is a very 

 rare one, and hitherto has only been found at the copper mines of 

 Boleo, near Santa Rosalia, Lower California. 



The specimen from Broken Hill is of an indigo blue colour, 

 crystallised in cubes with the angles replaced by planes of the 

 octahedron and the edges by those of the rhombic dodecahedron. 

 (See Plate 2.) The crystals vary from four to seven millimetres 

 along the edge, there are also embedded fragments of larger ones. 

 The cubes interpenetrate, similar to fluor spar. The matrix is 

 brown hsematite and quartz, some of the crystals are seated on the 

 haematite and others embedded in it. The hardness = 3*5; brittle. 

 Sp. Gr. = 5*02 at 15° C. The specific gravity was determined by 

 weighing fragments of the mineral in a very light stirrup pan in 

 distilled water on an Oertling's best chemical balance. The lustre 

 is strongly vitreous. 



Cleavage is nearly perfect parallel to the cube, and apparently 

 there is an imperfect octahedral cleavage as well. The fracture 

 is minutely conchoidal. Under the microscope it is seen to have 

 a striated structure in places. Heated quickly in a glass tube it 



