lawson.j Malignitc. 349 



constant feature. The mineral has the usual weak double refraction 

 of apatite, polarizing in blue grays of the first order. It is uniaxial 

 and optically negative. The crystals differ from the apatite micro- 

 lites usually observed as accessories in many rocks in the somewhat 

 uneven or obtusely serrate outline of the crystal boundaries. The 

 terminations of the prisms are often rounded. Fragments of the 

 mineral are easily isolated in a pure condition. These fragments 

 dissolve in hydrochloric acid, and when to the solution a minute 

 drop of sulphuric acid is added, a copious precipitate of characteris- 

 tic gypsum crystals is obtained. When fragments are dissolved in 

 nitric acid and treated with ammonium molybdate, the canary yel- 

 low precipitate indicative of phosphoric acid is obtained. The 

 specific gravity of the mineral as determined by the use of Klein's 

 solution is 3.250. The identification of the mineral as apatite is 

 thus placed beyond a doubt. 



The biotite calls for no special description, as it is very sparingly 

 represented in the rock, and exhibits the ordinary well-known char- 

 acters. As is usual with the mineral, its boundaries are irregular, 

 and have a corroded appearance. The titanite is quite accessory 

 to the general mineralogical composition of the rock, but occurs in 

 grains sufficiently large to permit of its positive identification. In 

 one slide a few grains of pyrite were detected, but the occurrence of 

 this mineral is quite exceptional. 



Chemical Characters. — An analysis of the rock was made for the 

 writer, by Mr. F. L. Ransome, Fellow in the Department of Geology 

 of the University of California, to whom the writer here desires to 

 express his obligations. The results of this analysis are given in 

 column I. Columns II, III, IV, V, and VI are analyses of Vesuvian 

 leucitophyres taken from Roth's tables,* while column VII is an 

 analysis of borolanite, taken from Teall's description of that rock.f 



*Beitrage zur Petrographie, etc. K. Akad. d. Wiss. Berlin, 

 f Loc cit. 



