QUARTZ. 



This is the most abundant, most dura- 

 ble and most indestructible of common 

 minerals. There is scarcely a sand 

 beach, field or mountain side upon which 

 this mineral cannot be found in some 

 form or other. Its abundance is due not 

 so much to its excess in quantity in the 

 underlying rocks as to the fact that, being 

 harder and less easily decomposed than 

 other minerals, it remains after they are 

 worn away. 



Though so common, it appears in so 

 great a variety of colors and different 

 kinds of structure that a large collection 

 of minerals looking very much unlike 

 might all be made up of Quartz. Tf they 

 were all of Quartz they would have the 

 following characteristics : Hardness, 7 

 (cannot be scratched with a knife blade) ; 

 specific gravity, two and a half times as 

 heavy as water ; no cleavage ; fracture 

 conchoidal (shell-like) ; infusible before 

 the blowpipe; insoluble in common 

 acids. The numerous varieties of Quartz 

 can be grouped into two classes, the 

 pheno-crystalline (plainly crystalline) 

 and the crypto-crystalline (obscurely 

 crystalline). This article deals with the 

 plainly crystalline varieties. These in- 

 clude, among other varieties, rock crystal, 

 amethyst, rose quartz, smoky quartz, and 

 sagenitic quartz. These varieties all oc- 

 cur in well formed crystals, and all have 

 a vitreous luster, i. e., luster like that of 

 glass. The differences between them are 

 almost exclusively differences of color. 



Rock Crystal — This is quartz in its 

 purest form. Typical rock crystal is per- 

 fectly transparent and colorless, but the 

 mineral is often more or less clouded 

 and opaque. By the ancients it was 

 supposed to be petrified ice, and 

 hence \hc Greeks applied to it their 

 word for ice, from which we get 

 ouv word crystal. The belief in its 

 ice origin survived to a comparativclv 

 late period, for in 1676 Rol)ert Roylc 

 opposed tlie idea, stating that the 

 quarlz could not ])c ice, first liccausc it 

 was two and a lirdf limes as heavy as 

 water, and sernnd Ix^ransc it was found 

 in In.pic-il conntric-s. 11ic l)clit>r of the 



ancients probably came largely from the 

 fact that the quartz they knew was ob- 

 tained from the peaks of the Alps. They 

 reasoned that it was ice that was frozen 

 so hard that it would never melt. Fortu- 

 nately our present knowledge of chemis- 

 try prevents us from any longer con- 

 founding the two substances, for we 

 know Quartz is oxide of silicon while 

 water is oxide of hydrogen. 



Quartz in the form of rock crystal oc- 

 curs in all parts of the globe, and for 

 the most part in well-formed crystals. 

 These crystals are usually six-sided, and 

 usually have the form of a prism capped 

 by a pyramid. Hot Springs, Arkansas, 

 and Little Falls, New York, are the best 

 known localities in our own country for 

 this form of crystallized quartz. The Lit- 

 tle Falls crystals are exceptionally bril- 

 liant and well formed. From this locality 

 and others the material, cut or uncut, is 

 often known as diamonds, and sold as 

 such. Such stones can, of course, be 

 easily distinguished from true diamond, 

 for while they will scratch glass, their 

 hardness is much below that of the king 

 of gems and they utterly lack the internal 

 fire of the latter. 



Rock crystal occurring in large, clear 

 masses is often cut into ornamental and 

 useful objects such as seals and paper- 

 weights, and especially into balls. The 

 latter industry flourishes especially in 

 Japan, and perfectly clear quartz balls 

 six inches in diameter are made there. 



Rock crystal is also used extensively to 

 cut into eyeglasses and spectacles in place 

 of glass, some considering it less detri- 

 mental to the eyes than glass. It is also 

 occasionally used for mirrors, it being su- 

 perior to glass for this purpose, in that 

 it does not detract from the rosiness of 

 the complextion. 



Among the ancients rock crystal was 

 much more highly prized than among us. 

 as it answered them many of the purposes 

 for which we now find glass more suita- 

 ])le and cheaper. Wine glasses were made 

 from it, though of course at great cost, 

 a tlK^usand dollars being considered a 

 small ])v\cc for 0110. Lenses (^f rock crys- 



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