Vol. 4] Murgoci. — Classification of the AmpMboles. 



367 



axes is variable, in Palache's specimens very large, so that the de- 

 termination of the optic character is not easy, but for blue plainly 

 negative ; Eosenbusch 's specimens show 2 V large, character neg- 

 ative; in some other rocks (see the material studied) I have 

 found crossite with quite small optic angle, character negative, 

 obvious in the orthopinacoidal sections. The sections perpendic- 

 ular to an optic axis may be recognized by their very intense 

 blue-violet color, of course with little or no pleochroism ; on ac- 

 count of the dispersion there is no extinction. 



The dispersion is so strong that it appears even in parallel 

 light; p>v; bp:c>bv (almost 6°). The hyperbola? which ap- 

 pear in convergent light in the sections near or perpendicular to 

 an optic axis are composed of several broad colored bands, red 

 and blue very distinct. 



A glaucophane with transverse axial plane (like crossite) has 

 been described by Michel Levy* in a schist of Versoix (Geneve). 

 The pleochroism is like crossite, in blue and violet, but the angle 

 of extinction only 3° ; the first, negative bisectrix almost perpen- 

 dicular to (100) . y—a = 0.021 ; y— = 0.003 ; 2V = 35° -40° ; 

 optic character negative. 



Another amphibole with the properties of crossite, except the 

 strong absorption, has been described by F. Beckef in a green 

 schist from Lammerbiichl (Duxer Thai). I have seen this min- 

 eral, and can state that only the intensity of the colors is differ- 

 ent. Pleochroism: C = dark blue to violet, b = dark greenish 

 blue, a = yellowish green. t) = C; b : C = -18° ca. ; bp-.cKb v : 

 c; 2V = 90°. y — a — O.Olca. The dispersion of the optic 

 axes p< v . All these properties are exactly the same as I have 

 determined for the crossite from the Coast Ranges of California. 

 Further, the origin and occurrence of Beeke's crossite is the 

 same as that from California. 



The analysis of Palache's crossite, made by W. S. Tangier 

 Smith, shows in comparison with Blasdale's analyses and those 

 by Washington, etc., of the glaucophane from Syra, Zermatt, etc., 



* In Barrois ' paper, Mem. sur les Schistes met. de 1 'ile de Groix. Ann. 

 Soe. Geol. du Nord, Lille, 1883, II., p. 50. 



t F. Becke. tiber cine merkwiirdige Hornblende. Tscherm. M. und 

 P. Mittheil, 21 p. 247, and Eosenbusch 's Mikroskopische Pkysiographie I. 

 II. A, p. 247. 



