774 



QUARTZ. 



leek-green by some substance not yet examined. 

 Heliotrope is likewise a variety of chalcedony, but 

 coloured by green earth, and occasionally dotted 

 with minute portions of red jasper. Iron flint con- 

 sists of quartz, intermingled throughout with oxide 

 of iron. The Compostella hyacinth is a red variety 

 of iron flint, in regular six-sided prisms, with py- 

 ramidal extremities, which occurs imbedded in 

 gypsum. Jasper differs from the two last varieties 

 in being massive, and in containing variable pro- 

 portions of clay. Red and brown jasper simply 

 allude to the colour of the compound. Striped 

 jasper appears to contain a larger portion of clay, 

 and is distinguished on account of its striped deli- 

 neations. Porcelain jasper is regarded as siliceous 

 slate altered by heat, and is found in the vicinity of 

 coal-mines. Those varieties which are found in 

 rounded masses, and which, from the concentric 

 layers of which they consist, appear to have been 

 formed in open spaces, are called Egyptian jasper. 

 Jasper agate consists of those varieties of jasper in 

 which several colours are so arranged as to produce 

 an agreeable effect. Mocha stone consists of agate, 

 containing appearances of vegetable filaments, 

 which have been occasioned through the infiltration 

 of iron and manganese through its crevices. Venus- 

 hair agate consists of quartz traversed by delicate 

 hair-shaped crystals of any kind. The most trans- 

 parent varieties of quartz are pure silex, which, ac- 

 cording to Berzelius, contains 49.70 silicon and 

 50.30 oxygen. Hornstone, flint and chalcedony 

 agree with it in composition. Several varieties 

 contain small quantities of alumine, lime, oxide of 

 iron, &c. Chrysoprase contains 0.01 oxide of nickel. 

 Quartz is infusible before the blow-pipe, and shows 

 itself to be pure silex. It is dissolved by soda 

 easily, and with effervescence. Two pieces rubbed 

 together emit an empyreumatic odour, and a phos- 

 phorescent light. Crystals of quartz may be obtained 

 from a solution of silica in fluoric acid, or in potash 

 diluted with water. The fluid from which crystals 

 of this species are formed, in geodes and other 

 natural cavities of rocks, has been observed to be 

 chiefly water. 



With respect to the distribution of quartz, and 

 which we have remarked above to be the most 

 abundant mineral known, it may be said that com- 

 mon quartz enters into the regularmixture of various 

 rocks, of granite, gneiss, mica slate, topaz rock, &c. 

 In others, it occurs in single crystals and in grains, as, 

 for instance, in porphyry, and is frequently met with 

 in the vesicular cavities of amygdaloidal rocks. In 

 these last situations, in particular, are found the 

 finest varieties of chalcedony, carnelian, of jasper 

 and agate. Hornstone forms globules and irregular 

 veins in compact limestone ; and flint occurs in a 

 similar manner, but disposed through vast beds of 

 chalk. Quartz, also, occurs in rocks, of which it 

 does not form a regular ingredient ; sometimes in 

 masses that are open in their interior, and lined 

 with crystals of enormous size. It also exists in 

 beds by itself, as in quartz-rock, and some varieties 

 of sandstone. Striped jasper and flinty slate form, 

 also, particular beds. The varieties, praseand chal- 

 cedony, as well as amethyst, are often found in beds 

 of iron ore. River sand, and that of extensive 

 plains, where it is sometimes so fine as to drift be- 

 fore the wind, are formed chiefly of quartz. Com- 

 mon quartz, and several other varieties, are spread 

 all over the earth, but certain varieties are confined 

 to a few localities. The finest and largest rock 

 crystals are found in the Alps of Salzburg, the Tyrol, 

 Switzerland, Dauphiny, Piedmont and Savoy ; also 

 in the isle of Madagascar, Ceylon and Brazil. 

 About 100 years ago, a great drusy cavity, lined 



with these crystals, was opened in Zinken, which 

 afforded 1000 cwt. of rock crystal, and, at that 

 early period, sold for nearly 7,000. One crystal 

 weighed eight cwt. ; others from four to five cwt. 

 The Alps furnish the handsomest specimens of 

 smoky quartz. This variety has, of late, been 

 brought, in large crystals and crystalline masses, 

 from Nova Scotia. The yellow quartz comes from 

 Brazil and Bohemia. A variety, intermediate be- 

 tween the smoky and the yellow, occurs at Cairn- 

 gorm, in Scotland. Amethysts, of various colours, 

 are brought from Brazil, but those of the finest 

 colours come from Ceylon, India and Persia. A 

 variety, intermediate between amethyst and smoky 

 quartz, is found in Siberia. Amethyst also abounds 

 in Transylvania and Hungary. Few localities of 

 this beautiful variety are known in North America. 

 Nova Scotia affords it in limited quantity ; and a 

 spot near Bristol, in Rhode Island, deserves to be 

 mentioned for the fine crystals it has produced. 

 Rose quartz occurs at Rabenstein, in Bavaria, and 

 in Siberia ; but no locality produces in so great 

 perfection as that at Paris, in Maine. Prase comes 

 from the mining district of Schwartzenberg, in 

 Saxony, and from Cumberland, in Rhode Island. 

 Smalt- blue chalcedony, sometimes in pseudo- 

 morphous crystals, occurs at Tresztyan, in 

 Transylvania ; the stalactitic shapes are found in 

 Iceland and the Faroe islands in amygdaloid, at 

 Huttenberg and Loben in Carinthia ; also in Hun- 

 gary, Scotland and Cornwall. Carnelian is brought 

 from Arabia, India, Surinam and Siberia. Chryso- 

 prase exists at Kosemutz, in Silesia, and at New- 

 fane, in Vermont. At this last-mentioned locality 

 are found small prismatic crystals of quartz, deeply 

 tinged by oxide of nickel. Chalcedony and carne- 

 lian are occasionally found, constituting very hand- 

 some agates, near Deerfield, in Massachusetts, and 

 and at Southbury, in Connecticut ; they are also 

 brought from Nova Scotia in each of which places 

 they occur in trap. Plasma is found in Moravia, 

 and in Bavaria. Flint is common in England, 

 France, Poland, and Spain. Hornstone is abundant 

 in many countries. Flinty slate forms beds, and 

 occurs in pebbles, in Bohemia, Silesia, Saxony, in 

 the Western States of the United States, and in the 

 Canadas. Fibrous quartz is found in the Hartz ; 

 cat's eye in Ceylon, and the coast of Malabar ; and 

 avanturine at the cape de Gat, in Spain. Heliotrope 

 was formerly brought from Ethiopia, but is now 

 generally obtained from Bucharia, from Tartary, 

 and Siberia. Iron flint, or ferruginous quartz, is fre- 

 quent in the iron-stone veins of Saxony, Bohemia, 

 Hungary, Transylvania, &c. The Compostella 

 hyacinth occurs near Compostella, in Spain. Striped 

 jasper is found in Siberia, atGrandtstein, in Saxony, 

 at Ivybridge, in Devonshire ; the brown Egyptian 

 jasper comes from the banks of the Nile ; the red 

 variety from Baden, also from the town of Saugus, 

 near Boston, in Massachusetts. 



Several varieties of quartz are of important use in 

 the arts and manufactures, and have long been 

 employed for purposes of decoration and utility by 

 mankind. The ancients regarded rock crystal as 

 petrified water ; they esteemed it, particularly, for 

 the fabrication of vases, especially when it could be 

 procured in large pieces. Such were the two cups 

 which Nero dashed to pieces when he received the 

 news of the revolt which caused his ruin, one of 

 which had cost him a sum equal to 675. At pre- 

 sent, it is esteemed, not only for cups, urns, chan- 

 deliers, but for seals, spectacle glasses, and optical 

 instruments. Amethyst takes a fine polish, and is 

 much employed in jewelry. Its colour, when dark 

 blue, is well adapted to that of gold, in which metal 



