Blasdale.] 



Contribution to Mineralogy. 



337 



typical glaucophane Bodewig found 124° 51'. Strongly-developed 

 prismatic cleavages are shown in all sections of the mineral. 



Optical Properties. — From some of the most perfect crystals sec- 

 tions were cut parallel, or as nearly so as the nature of the material 

 would permit, to the clino- and orthopinacoids. The former 

 extinguished light at an angle of 8° with the cleavage trace and in 

 convergent light gave no interference figure. This position was 

 shown by the use of a quarter-undulation mica plate and also of a 

 plate of gypsum, both of known orientation, to be the direction of 

 least elasticity, in which respect the mineral differs from crossite 

 and agrees with glaucophane, though the extinction angle is 

 greater by two degrees than in any specimen of that mineral which 

 has been examined thus far. Sections cut parallel to the orthopin- 

 acoid gave parallel extinction, and with convergent light gave only 

 a broad brush of interference colors. The optical orientation is, 

 therefore, the same as that found in the majority of hornblendes, 

 that is, C:c = 8°, though in the absence of terminal crystallographic 

 planes the exact position of C can not be determined. The pleo- 

 chroism is the most pronounced optical feature of the mineral and 

 furnishes the most valuable criterion for its identification. The 

 color of the C ray is bright sky blue to deep blue, of 6 purple to 

 violet, and of colorless, or a very faint yellow. In these respects 

 the mineral closely resembles glaucophane, but differs from crossite. 

 In some crystals certain localized areas presented a light green 

 color, probably due to the presence of actinolite, though no very 

 definite line of separation from the main portion of the crystal 

 could be distinguished. 



Cheinical Properties. — A portion of the first-described specimen 

 was crushed in an agate mortar, and treated with hydrochloric acid, 

 washed, and dried, and that portion which passed through an eighty- 

 but was retained by a one-hundred mesh sieve, separated from the 

 remaining titanite by means of Klein's solution. The purified 

 material had a specific gravity of 3.1 19. The second specimen was 

 ground for analysis without further preparation; it gave a specific 

 gravity of 3. 1 16. The finely-ground material, which is of a blue- 

 gray color, fused readily with the formation of a dark glass, and 

 was scarcely attacked by strong acids even after long boiling. 



