140 DESCRIPTION AND ANALYSIS OF YENITE. 



Porphyiy. 5. A porphyry with base of white compact feldspar, and 



containinsif black globular nodules, which appear to me to be 

 a mixture of amphibole and feldspar. 



Diallage. 6. Green and metalloid diallage. 



Resiuite. 7, Resinite quartz similar to that of Musinet in Pied" 



mont. 



Fetid quartz, 8. Fetid pseudoraorphous qua>Ptz, &c. 



In some future papers I shall mention what I have noticed, 

 that is peculiar, either in the characters or situations of these : 

 but I shall confine myself for the present to that, which I 

 now lay before the class, and to which I have given the name 



Yenite. of yenile, from of one of the most memorable events of the 



age, the battle of Jen^. 



Its physical characters. 



Spec. grav. This mineral weighs nearly four times as much as distilled 



water (3-825, 3-97-t, 3-985, 4-06l). 



Hardness. Its hardness is a little inferior to that of the adularia feld- 



spar, by which it is scratched ; but it scratches glass strongly, 

 and gives a few sparks ',vith steel. 



Primitive for.n . The mechanical division leads, as will be more particularly 

 described presently, to a rhomboidal prism of 113" and 67% 

 which may be subdivided parallel to the shorter diagonals of 

 its bases. 



Colour. The yenite is opake, and of a black colour inclining some- 



times to brown. Its pouder is of the same hue. 



Surface. The surface of the crystals, when they are very black, is 



shining. (Those varieties represented PI. IV, figs. 5 and 6, 

 have commonly a dull and brownish surface.) The lateral 

 faces of the prisms are streited lengthwise: the facets O of 

 the summit are smooth and very shining. 



Fracture. The fracture is unequal, and of a greasy lustre (nearly 



like that of phosphate of manganese). 



Nonelectric. It is not electric, either by heat or friction. 



Ma'-netic Heated to redness in the flame of a wax candle merely, it 



when heated, becomes weakly attractable by the magnet. 



Spontaneously Exposed to the action of the air it is decomposed, and 



decomposed, covered with an earthy yellow and brown crust, perfectly si- 

 milar to the ochres, or oxides of iron mingled with earths, 

 which are found native. 



Geometrical 



