MINERALS. 



HORNBLENDE.— A mineral 

 species, placed by Dana in the 

 augite section of the anhydrous 

 silicates. In common use the 

 name is limited, as it was formerly ap- 

 plied only to the dark crystalline 

 minerals which are met with in long, 

 slender prisms, either scattered in 

 quartz, granite, etc., or generally dis- 

 seminated throughout their mass. The 

 color of the mineral is usually black 

 or dark green, owing to the presence 

 of much iron. It appears to have been 

 produced under conditions of fusion 

 and cooling which cannot be imitated 

 in the laboratory, the crystals obtained 

 artificially being of augite type. 



Malachite.— One of the native car- 

 bonates of copper. It is sometimes 

 crystallized, but more often occurs in 

 concretionary masses of various shades 

 of green, which are generally banded 

 or arranged in such a manner that the 

 mineral, which takes a fine polish, is 

 much prized as an ornamental stone. 

 Great quantities of it are found in the 

 Siberian mines, and many beautiful 

 objects are manufactured from it. 



Quartz.— The most abundant of all 

 minerals, existing as a constituent of 

 many rocks, composing of itself the 

 rock known as quartzite or quartz 

 rock and some of the sandstones and 

 pure sand, forming the chief portion 

 of most mineral veins. In composi- 

 tion it is silica, and when uncontami- 

 uated with any foreign intermixture it 

 appears in clear, transparent crystals 

 like glass or ice. Pure quartz is largely 

 employed in the manufacture of glass 

 and is commonly obtained for this pur- 

 pose in the form of sand. Quartz veins 

 with few exceptions form the gangues 

 in which gold is found. 



Tourmaline.— A name applied to a 

 group of double silicates, composed of 

 many other minerals. The color of 

 tourmalines varies with their compo- 

 sition. The red, called rubellite. are 

 manganese tourmaline containing lithi- 

 um and manganese, with little or no 

 iron; the violet, blue and green contain 

 iron, and the black are either iron or 



magnesium- iron tourmalines. Some- 

 times the crystals are red at one ex- 

 tremit)' and green at the other, or green 

 internally and red externally, or vice 

 versa. Pink crystals are found' in the 

 island of Elba. Tourmalines are not 

 often used in jewelry, although they 

 form beautiful gems and bear a high 

 price. A magnificent group of pink 

 tourmalines, nearly a foot square, was 

 given by the king of Burmah to Col. 

 Sykes, while commissioner to his court. 

 The tourmaline appears to have been 

 brought to Europe from Ceylon by the 

 Dutch about the end of the seven- 

 teenth century, and was exhibited as a 

 curiosity on account of its p}ro- elec- 

 tric properties. 



Agate. — Of the quartz family, and is 

 one of the modifications in which silica 

 presents itself nearly in a state of 

 purity. Agates are distinguished from 

 the other varieties by the veins of dif- 

 ferent shades of color which traverse 

 the stone in parallel concentric layers, 

 often so thin as to number fifty or more 

 to an inch. Externally the agates are 

 rough and exhibit no appearance of 

 their beautiful, veined structure, which 

 is exposed on breaking them, and still 

 more perfectly after polishing. Though 

 the varieties of agate are mostly very 

 common minerals in this countiy as 

 well as in the old world, those locali- 

 ties only are of interest which have 

 long been famous for their production 

 and which still furnish all the agates 

 required b)' commerce. 



Amethyst. — So named because it 

 was supposed by the ancient Persians 

 that cups made of it would prevent 

 the liquor they contained from intoxi- 

 cating. The stone consists of crystal- 

 lized quartz of a purple or blue violet 

 color, probably derived from a com- 

 pound of iron and soda. The color is 

 not always diffused through it, and is 

 less brilliant by candlelight. 



Serpentine. — Serpentine differs in 

 composition from the other marbles. 

 It is a soft mineral of different shades 

 of green, of waxy luster, and suscept- 

 ible of a high polish. It is better 



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