1893.] NATURAL SCIENCES OF PHILADELPHIA. 175 



grayish-green. Apparently it is amorphous raacroscopically, in 

 reality crystallized in fine fibres which lie in all directions as if 

 felted together. The crystals as seen under the microscope are 

 mostly very thin and appear colorless, but those which are thicker 

 show a green color and with one nicol prism ; when the object is 

 rotated, a second color, yellow, is observed. The thicker crystals 

 are therefore dichroic. These latter, when viewed parallel with the 

 orthodiagonal plane, show this dichroic property particularly, but it 

 is extinguished parallel to their longer axis, between the crossed 

 nicols. The extinction parallel to the clinodiagonal I determined 

 to be equal to — 28°. The color of interference of this latter plane 

 was a bright yellow, but parallel to the orthodiagonal it was blue. 

 These optical characters indicate that this variety of amphibole is 

 monoclinic. 



The hardness is not determinable. Specific gravity=2 - 6. 



Heated in the oxidizing flame it assumes a rusty color, fusing with 

 difficulty to a black mass; in the reducing flame it becomes gray. 

 With the fluxes iron and silica are indicated. 



The analytical result was as follows : 



Si0 2 48*45 per cent. 



Fe 2 3 33*90 per cent. 



CaO 11-80 per cent, 



MgO 6-23 per cent. 



A trace of manganese was observed but not determined quantita- 

 tively. 



The composition of byssolite of Saussure is nearly the above, but 

 this variety occurs as stiff, shining, bristle-like crystals, not felt-like 

 as is the case with the dull, soft material under discussion. At any 

 rate it is but a variety of amphibole and compares better with the 

 Scandinavian mineral asbeferrite. 



Cacoxenite. This species occurs on limonite atBeartown, Lan- 

 caster Co., Penna. The reddish-yellow radiating tufts are made up 

 of very fine, fragile crystals whose hardness cannot be determined. 

 It is entirely soluble in nitric acid, and the solution gives reactions 

 for phosphoric acid and iron. It also contains water. 



Beneath the microscope the orthorhombic forms are clearly 

 observable, as (110) (001). They are dichroic; gray when parallel 

 with the lower nicol and yellow when at a right angle to it. Between 

 the crossed nicols superb interference colors of orange, yellow, blue 

 and violet appear. This seems singular because the crystals do not 



