KNOPF: ANDALUSITE MASS 551 



canyon on the north and by the cliffs on the west, it extends to 

 a depth of at least 300 feet. 



On the east side of the mass is a great body of coarse milk- 

 white quartz, which in places is as much as 50 feet wide Veins 

 and stringers of this quartz penetrate the andalusite mass for 

 long distances. It is notable that the narrower stringers of 

 quartz carry considerable quantities of the deep-blue mineral 

 lazulite; muscovite also is common in the quartz but is not 

 abundant; and specular hematite is locally abundant. The 

 lazulite, a hydrous phosphate of aluminum, magnesium, and 

 iron carrying about 45 per cent of P2O5, is of course a striking 

 constituent, because of its uncommon and intense color, and 

 in fact it was the presence of this mineral that led to the dis- 

 covery of the andalusite mass. The prospector who found the 

 lazulite thought it was bromide of silver, but when an assay 

 showed that it contains no silver, his interest in it vanished. 

 Later, others located and staked the andalusite mass, under the 

 belief that the great body of brown rock traversed by the lazu- 

 lite-bearing quartz veins is apatite. 



Andalusite rock, consisting wholly of coarsely granular an- 

 dalusite and free from quartz stringers, occurs on the northwest 

 side of the deposit. The texture of rock of this kind ranges 

 from coarsely granular or radial columnar to roughly schistose. 

 The schistose structure is more and more well-defined toward 

 the east border and is due to the increasing amounts of quartz 

 and finely flaky muscovite that occur with the andalusite. The 

 andalusite-bearing rock probably grades into the volcanic 

 porphyry on the east. Under the microscope the andalusite 

 is found to have the normal optical properties of that mineral. 

 In habit it is notably poikilitic and spongiform where much 

 quartz is present, and in such places the anhedrons of andalusite 

 inclose large numbers of quartz grains. Dr. W. T. Schaller 

 has measured the refractive indices of the mineral, finding 

 them to be: y = 1.642, p = 1.635, and a = 1.631. Moreover 

 chemical examination by Dr. Schaller shows that the mineral 

 contains only alumina and silica; and the identity of the min- 

 eral as andalusite is therefore fully established. 



