384 



University of California Publications. 



[Geology 



green amphiboles, uniaxial or with transverse axial plane, be- 

 long ; these amphiboles are described in the literature, and I was 

 fortunate enough to find some in the rocks studied. 



If the relation between Fe 2 3 and optic properties exists also 

 in the karinthine group (as I have tried to prove above) as in 

 the glaueamphiboles, then the following amphiboles with trans- 

 verse axial plane must be very rich in Fe 2 3 . 



Laneite (n. v.). — As far as I know. Dr. A. C. Lane was the 

 first to make known (in 1895, in a letter to Dr. C. Palache) an 

 amphibole with transverse axial plane in a theralite from Michi- 

 gan ; at the same time he suggested that there might be an am- 

 phibole which was uniaxial, or even for a definite composition 

 isotropic ; he connected this phenomenon with the amount of Na. 

 Some hornblendes with very weak birefringence (nearly iso- 

 tropic) have been described by Milch,* and hastingsite with 

 Al 2 Oa: Fe 2 3 = ll:8; C:c = 25°-30°; 2E = 30°-45°, optic 

 character negative, a = yellowish green; b = C = deep blue- 

 green, by F. D. Adams and J. Harrington. f Such blue-green 

 hornblendes with very small optical angle have been often men- 

 tioned as occurring in the alkali rocks. Dr. C. HlawatschJ has 

 described a uniaxial amphibole as occurring in the gabbro-diorite 

 from Jablanica (Bosnia) a — deep yellowish brown, b = C = 

 deep blue-green; C:c = 18°, 2 V = 40°-()° (in the blue horn- 

 blende, in the brown one very large). He considers it as inter- 

 mediate between the common hornblende (with the axial plane 

 parallel to 010) and the hornblende with transverse axial plane 

 which he himself has found in the eleolite syenite porphyry from 

 Viezzena Thai (Predazzo) : ft = light yellow, b = dark blue- 

 green, C = dark brown-green, b :c = 25° ; 2 V — 45° ; optic char- 

 acter negative. 



It is a pity that these hornblendes, as well as the following, 

 have not been analyzed; very probably they belong to the sore- 

 tite or barkevikite type, and are very rich in Fe 2 3 . Optically, 



* Milch, Die Schiefer des Taunus, Zeitsckr. d. D. Geol. Gesellseh., XLI, 

 pp. 394 and 423. 



t Fr. D. Adams and B. J. Harrington, Amer. Jour. Sei., I. 189G, p. 210. 

 Also in Bosenbuseh. 



t C. Hlawatsch, Tscherm. Mittheil., 1903, p. 499, 4. Ibidem, XX, p. 43. 



