A. F. Rogers — Baddeleyite from Montana. 55 



Crystal Form. — The baddeleyite crystals are square-pris- 

 matic or tabular-prismatic in habit with only one well-defined 

 zone with the forms {100}, :110;. and [010}. Eight crystals 

 were measured on the reflection goniometer with indifferent 

 results, the angle for (100 : 110) varying from about 44 = to 46°. 

 Finally, one crystal was found which gave the following meas- 



nrements : 













Average 



Calc. 



100 : 110 



44° -22', 44 c 25', 44 c '2 6' 



44 : 24' 



44 : 20' 



110 : 010 



45° 31', 45 c 35', 45 = 38' 



45 D 35' 



45 c 40' 



100 : 010 



S9 C 57', 90 c 0', 90° 0' 



89° 59' 



90 c 0' 



The calculated 



angles established bv 



Blake and 



Smith- are 



given in the last column. 



For the angle (100 : 110) Fletcher gives U : 0' and Hussak. 

 44° 17-J'. The terminal faces are obscure and rounded, but on 

 one crystal faces of the form_ fill} were identified by the fol- 

 lowing measurements, (010 : 111) = 63° 15' (average of 62° 30' 

 and 64° 0'), the calculated value according to Blake and Smith 

 being 64° IS 7 . 



Physical Tests. — The cleavage seems to be in four direc- 

 tions, parallel to {100;. {110}, and {010}. The hardness is 

 about 6-J-, for it scratches glass faintly and in turn is scratched 

 by quartz. The luster is submetallic or metallic adamantine. 

 The color is black, but in fragments it is translucent brownish 

 red. The double refraction is strong, and the index of refrac- 

 tion is greater than that of methylene iodide. Some fragments 

 show several sets of twinning lamella? crossing each other. In 

 thin-sections the baddeleyite appears as elongate crystals with 

 almost parallel extinction and slight pleochroism, the greatest 

 absorption being parallel to the length of the crystal. 



Pyrognostic Tests. — The mineral is practically infusible 

 when heated before the blowpipe, but examination with a 

 high-power microscope shows a slight sprouting on the edges. 

 In the oxygen-gas blowpipe^ it is fairly easily fusible to a 

 black globule. In the closed tube it is unaltered. When 

 heated in the platinum forceps it glows with a brilliant light, 

 which recalls the fact that zirconia is the principal constituent 

 of the filament of the Xernst lamp. 



Chemical Tests. — In fine powder the baddeleyite is insoluble 

 in a sodium metaphosphate bead but is soluble in a borax bead 

 giving a faint iron test. It is insoluble in aqua regia but is 

 decomposed by strong sulphuric acid. The hydrochloric acid 

 solution of the soda fusion turns turmeric paper orange, and 

 since no green flame was obtained with boracic acid flux this 



* Mineralogical Magazine, vol. xiv. p. 378, 1907. 



\ See Lnquer. Sell. Mines Quart., vol. sxix. p. 179. 1908. 



