QUARTZ. 



The crypto-crystalline (obscurely crys- 

 talline) varieties of Quartz are many. 

 The following may be named as the most 

 important: Chalcedony, carnelian, sard, 

 chrysoprase, prase, plasma, bloodstone, 

 agate, onyx, sardonyx, jasper, basanite, 

 flint and hornstone. The distinctions be- 

 tween the different varieties • are loose 

 and are differently stated by different au- 

 thorities. Some class agate, onyx, sard- 

 onyx, plasma and carnelian together as 

 varieties of chalcedony, while others con- 

 sider chalcedony a simple variety. The 

 chalcedonic varieties of quartz agree in 

 having a fibrous structure and in being 

 somewhat softer (hardness 6^) and 

 somewhat lighter (specific gravity 2.6) 

 then crystallized quartz. They also 

 break with more difficulty than quartz, 

 being very tough. The varieties differ 

 among themselves, chiefly in color. 



Common chalcedony has a waxy luster 

 and is usually translucent rather than 

 transparent. The transparent forms are 

 known as "oriental," the translucent as 

 ''occidental" chalcedony. Common chal- 

 cedony has little color, shades of gray 

 and blue being the most common, al- 

 though other tints occur. It usually pre- 

 sents rounded surfaces which have grape- 

 like, kidney-like or stalactitic forms. It 

 occurs coating other rocks or minerals 

 or lines cavities or fills veins and clefts. 

 It is never, so far as we know, deposited 

 in any other way than by percolating 

 waters. At Tampa Bay, Florida, the 

 waters containing chalcedony have pene- 

 trated corals and preserved them, often 

 giving forms showing the shape of the 

 coral outside and a cavity within. 

 Throughout the "Bad Lands" of the 

 West, clefts in the hills are often filled 

 with sheets of chalcedony varying in 

 thickness from that of thin paper to 

 nearly an inch. These chalcedony veins 

 ramify in all directions and often extend 

 for many rods without interruption. 



When the chalcedony is penetrated by 



branching forms of manganese or iron 

 oxide the forms known as "mocha 

 stones" and "moss agates" are produ'ced. 

 These are not due to vegetation any 

 more than the similar forms of frost on 

 our window panes. They are purely 

 mineral in their origin. Moss agates 

 are found in numerous localities in the 

 States of Utah, Wyoming, Colorado and 

 Montana. In the opinion of Mr. George 

 F. Kunz "no stone that is used in jewelry 

 in the United States is cheaper, more 

 beautiful or more plentiful than the moss 

 agate." The best occur as rolled pebbles 

 in the beds of streams. The name, 

 "Mocha stone," sometimes applied to 

 moss agates is either due to the fact 

 that those first used came from Mocha 

 in Arabia, or it is a corruption of the 

 word moss agate. The finest moss agates 

 now known come from India. A white 

 variety of chalcedony containing minute 

 blood red spots is known as St. Stephen's 

 stone. Chalcedony was formerly used 

 much more and more highly prized than 

 at the present time. It was especially 

 employed for seals and rings, but also 

 for plates, cups and vases. These were 

 often engraved in the most elaborate 

 manner, the hardness and toughness 

 of the stone making it well adapted for 

 this purpose. The sentiment of the stone 

 is : "A disperser of melancholy." The 

 name chalcedony is from Chalcedon, a 

 city in Asia Minor, where the original 

 chalcedony was found. This mineral 

 was probably not like our modern chal- 

 cedony, however, being more probably 

 a green quartz. This chalcedony is men- 

 tioned as one of the foundation stones of 

 the Holy City in the Book of Revela- 

 tions. 



Carnelian is a red variety of chalce- 

 dony, sard a brown variety. All grada- 

 tions between these shades of course oc- 

 cur, those of the reddish cast being the 

 most common. The most highly prized 

 color for carnelian is a deep blood red, 



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