286 



DESCRIPTIVE MINERALOGY. 



PYROXENE. 



[From the Greek fvp, fire, and Jevos, a stranger ; because it was found in lava, to which Haiiy consi- 

 dered it as not belonging.] 



Augite. CkaveUmd and Phillips. — Paratomous Augite. Jamescn. — Paratomcr Augit-Spath. Mohs. — Pyroxene. 



Shepard and Dana. 



It includas Augite, Diopside, Mussitc, Sahlite, Fassaite, Baikilitc and CoccoUte. Dr. Thomson makes a distinct spe- 

 cies of White Aucite, which includes Diopside, Mussite, Alalite, Sahlite and MalacoUte. The rest are united under his 

 Pyroienc. 



Beudant has a subgenus Pyroxene, under which he arranges as distinct species, Diopside, which includes the white 

 and light green varieties ; Hcdenbergite, comprising those which are dark green and black ; Pyrodmalite and Hyper- 

 sthene. Between the two first it is, however, exceedingly difficult to draw the line of specific distinction. 



, 102. 



Description. Colour green, black and brown ; also grey and white. 

 It occurs regularly crystallized ; also in grains, and amorphous. The 

 primary form is an oblique rhombic prism. Fig. 192. M on M' 87° 

 5"; M or M' on P 100° 10' or 100° 25'. Cleavage parallel with M 

 rather perfect, but interrupted ; in some varieties, it is very perfect in 

 the direction of P. Fracture conchoidal and uneven. Lustre varies 

 from vitreous to resinous. Ranges from transparent to opaque. Hard- 

 ness from 5 . to 6.0. Specific gravity from 3 . 20 to 3 . 50. Before 

 the blowpipe, it fuses, emits a few bubbles, and finally yields a glassy 

 globule, more or less tinged by iron. It is readily soluble with borax. 

 Several varieties of pyroxene have been obtained artificially by means 

 of fusion. 

 Pjnroxene often resembles hornblende, but can be distinguished by the difference in its 

 crystalline form, and in its behaviour before the blowpipe. 



Varieties. The following varieties of this mineral deserve to be particularly noticed : 



Diopside — White Augite — Mussite — Alalite. This variety is generally crystallized. 

 The colour is white or pale green. Translucent or transparent. The primary is an oblique 

 rhombic prism, of the same form and measurement as that of pyroxene. Before the blow- 

 pipe, it fuses into a colourless semi-transparent mass ; with borax, into a diaphanous glass. 



Pyrgom — Pyrogome — Fassaite. I'his is generally of a dingy green colour ; assumes 

 nearly the same crystalline form, and yields to mechanical division parallel to the lateral planes 

 of a prism of the same measurements as that of pyroxene. 



Sahlite — MalacoUte — Baikilite. It occurs in prismatic crystals of four or eight sides, 

 with inclined summits. It is of a greenish grey colour. It often occurs massive. The 

 structure is lamellar, and it has the same primary form as the preceding. 



Common Augite — Conchoidal Augite. This includes all the varieties in which the colours 

 are dark green and black, with a conchoidal and uneven fracture, and a resinous lustre. It 

 is opaque or faintly translucent on the edges. 



