24:6 DESCRIPTIONS OF MINERALS. 



tions — the light colored, the dark colored, and the thin 

 foliated. 



I. Malacolite or white augite is a calcium magnesium 

 pyroxene, and includes white or grayish-white crystals or crys- 

 talline masses. Diopside, of the same composition, occurs in 

 greenish- white or grayish-green crystals, and cleavable masses 

 cleaving with a bright smooth surface. Salilite contains 

 iron in addition, and is of a more dingy green color, has less 

 lustre and coarser structure than diopside, but is otherwise 

 similar ; named from the place Sahla, where it occurs. 

 Fassaite contains a little alumina in addition to the ele- 

 ments of sahlite, and is found in crystals of rich green shades 

 and smooth and lustrous exterior. The name is derived 

 from the foreign locality Fassa. Coccolite is a general name 

 for granular varieties, derived from the Greek coccos, grain. 

 The green is called green coccolite, the white, white coccolite. 

 The specific gravity of these varieties varies from 3*25 to 3*3. 



Asbestus. This name includes fibrous varieties of both 

 pyroxene and hornblende ; it is more particularly noticed 

 under the latter species, as pyroxene is rarely asbestiform. 



II. Augite includes the black and greenish-black crystals, 

 which contain a larger percentage of iron, or iron and mag- 

 nesium, and which mostly present the form in figure 1. Spe- 

 cific gravity 3*3-3*4. This is the common pyroxene of erup- 

 tive rocks. Hedenbergite, an iron-calcium pyroxene, is a green- 

 ish-black opaque variety, in cleavable mosses affording a 

 greenish-brown streak ; specific gravity 3 '5. Polylite, Hud- 

 sonite, and Jeffersonite, fall here ; the last contains some 

 zinc oxide. These varieties fuse more easily than the pre- 

 ceding, and the globule obtained is colored black by the 

 iron oxide. 



III. DiaUage is a thin-foliated variety, often occurring 

 imbedded in serpentine and some other' rocks. It differs 

 from bronzite and hypersthene in crystalline form, and in 

 being fusible. 



Obs. Pyroxene is one of the most common minerals. It 

 occurs in almost all basic eruptive rocks, like doleryte, as an 

 essential constituent, and is frequently met with in rocks of 

 other kinds ; common also in granular limestone. In basalt 

 the crystals are generally small and black or greenish black. 

 In the other rocks, they occur of all the shades of color 

 given, and of all sizes to a foot or more in length. One crys- 

 tal from Orange County, measured 6 inches In length, and 



