554 Palache and Warren — Chemical Composition and 



been of rather late formation and is particularly associated 

 with aegirite ; as embedded xenomorpnic plates, and groups 

 of tiny crystals implanted on crevices of fractured aegirite 

 crystals (Ballon quarry) ; and as clusters of larger crystals upon 

 the walls of cavities left by the destruction of such crystals by 

 magmatic resorption (Fallon quarry). The crystals are small, 

 not exceeding a diameter of 2"" n , and are always very thin tab- 

 ular in habit. A dull-black coating of manganese oxide com- 

 monly gives them a lusterless appearance, but in two specimens 

 brilliant crystals were obtained which, despite minute size, 

 gave good measurements on the goniometer. Octahedrite is 

 almost always sparingly present with ilmenite. 



The forms _observed are as follows: c(0001), m(1010), 

 «(1120), (2130)* 8(1019), w(10U), £(2025), r(lOll), 

 /10.7.7.20), e(0112), A (0445)*, 6-(0221), X (0552)*, gr (0.3.3.11)*, 

 h (0.3.3.10)*, tt(1123), ?i(2243). 



The crystals from Ballon quarry showed the forms c, m,a, 

 8, r, and 7r,, the prism zone being well developed and the base 

 large and very brilliant. The prism is new to ilmenite. 



Crystals from Fallon quarry are doininantly rhombohedral, 

 prism faces being reduced to mere lines. The crystals meas- 

 ured showed the following combinations : 



]. 



2. 



> 



, '>; f, e, 



, , r, k. 



s, 



3. 



c, 



m, r, u, e, 



k, 



4. 



c, 



771, 7\ 71. 





5. 



1 



r, e, g, 7%. 





6. 



c, 



771, 7; e, n. 





n. 

 n. 



7. C, It, 7\ 



As shown in the figures (figs. 8 and 9), flat positive rhombo- 

 hedrons are largely developed on these crystals, recalling the 

 description of one (the common) phase of " Crichtonite " from 

 Oisans by Des Cloizeaux.f That_ author considered the rhom- 

 bohedrons which he measured (1015), and (1019), and (1.0.1.11) 

 as negative, but left the determination of sign doubtful. The 

 second of these forms is common to all the crystals from Fal- 

 lon quarry and is certainly positive, so both the others should 

 be likewise so considered. Several negative rhoinbohedrons 

 new to ilmenite were observed and are based on the following 

 data : 



Form Calculated Measi 

 <j> p <p 



g (0.3.3.11) 30°00' 23°34' 30°00' 



k (0.3.3.10) " 25 27 " 



A (0445) " 51 59 " 



A (0552) " 75 57 " 



8 (2130) 10 53 90 00 10 30 



* New forms. t Mineralogie, ii, 222, 1893. 



ired 



No. 



Limits of p. 



P 

 23°46' 

 25 34 

 51 57 

 76 06 

 90 00 



3 

 1 



2 

 1 

 4 



23°28' to 24°05' 

 51 53 to 52 00 

 10 36 to 11 34 



