116 ransome: albitite dikes 



The mineral noted as occurring in small glittering specks does 

 not give any clear indication of its crystal form in thin section; 

 but particles obtained by crushing the rock and concentrating the 

 powder by panning, when examined under the microscope, show 

 that the mineral has at least one perfect cleavage, that its luster 

 is metallic-adamantine and that it crystallizes for the most part 

 in acute, distorted, tetragonal pyramids, apparently the unit 

 form, with strong transverse striations. A few, more regular 

 forms were also observed in which the striations are limited to the 

 equatorial zone of the crystal. The color by transmitted light 

 is yellow to chestnut brown, with notable absorption in directions 

 transverse to the prism axis. The index of refraction is high and 

 the birefringence strong. Particles tested chemically by Mr. W. 

 T. Schaller gave a strong reaction for titanium, which, with such 

 crystallographic and optical data as have been recorded leaves 

 little doubt of the identity of the mineral as anatase The crys- 

 tals, none of which is over a millimeter in length, occur embedded 

 in all of the other constituents of the rock save apatite and zircon, 

 which are the other accessory minerals present With the apatite, 

 moreover, it appears to have projected into the cavities now occu- 

 pied by calcite. 



Anatase is not a common rock constituent, and, where present, 

 has generally been considered as a product of alteration. In these 

 dikes, however, the mineral is apparently original for alt ho 

 many of the crystals are enclosed in calcite others are embedded 

 in fresh albite and in quartz. 



A chemical analysis of a specimen of rock from one of the dikes 

 near the nickel mine in Cottonwood Canyon is as follows: 



Chemical analysis of (libit ih 



George Steiger, analyst 



Si0 2 61.71 H 2 0- 51 



A1 2 3 16.63 H 2 0+ 0.81 



Fe.,0,\ Q ^ Ti0 2 0.79 



FeO / ' Zr0 2 0.04 



MgO none Ca0 2 4.05 



CaO 5.94 P.,O s 0.15 



Na 2 8.52 • 



K,0 0.16 99.71 



