THE PROPERTIES OF MINERALS. 657 



ancewith chemical laws and grouped under certain ])r()inin(Mit types as 

 follows : 



Native elements. — Of the seventy or more elements at present known 

 to chemistry, but eighteen, excluding those occurring only in the 

 gaseous state, are found native; carbon, sulphur, the metals of the 

 platitium group, mercury, copper, silver, and gold are among these. 

 With the native elements are included the native alloys or compounds 

 and mixtures of elements belonging to the same groups in the periodic 

 system. 



The type is represented by the following specimens: 



Graphite— Ceylou. (Cat. No. 81365, U.S.N.M.) 

 Sulphur— Cianciana, Sicily. (Cat. No. 51951, U.S.N.M.) 



Selensulphur — White Islands, Bay of Plenty, New Zealand. (Cat. No. 48050, 

 U.S.N.M.) 

 Tellurium — Keystone Lode, Boulder County, Colorado. (Cat. No. 946H, U.S.N.M.) 

 Arsenic— near Loadville, Colorado. (Cat. No. 81824, U.S.N.M.) 

 Allemontite— Alleniont, France. (Cat. No. 46395, I'.S.N.M.) 

 Antimony— Prince William, New Brunswick. (Cat. No. 45704, U.S.N.M.) 

 Bismuth— Schueeberg, Saxony. (Cat. No. 45415, U.S.N.M.) 

 Iron— Ovifak, Disco Island, Greenland. (Cat. No. 47480, U.S.N.M.) 

 Copper— Ontonagon County. Michigan. (Cat. No. 18227, U.S.N.M.) 

 Silver— Freiberg, Saxony. (Cat. No. 49478, U.S.N.M.) 

 Gold— California. (Cat. No. 81429, U.S.N.M.) 



Fluorides, chlorides, bromides, and iodides. — The halogens, fluorine, 

 chlorine, bromine, and iodine, form simple and complex compounds 

 with other elements. The halides, as these compounds are called, are 

 divided cliemically into four classes — fluorides, chlorides, bromides, and 

 iodides — according to the nature of the negative constituent. Two 

 of the halogens — fluorine and chlorine — enter into the composition 

 of several oxidized species, called, respectively, oxyfluorides and oxy- 

 cldorides — compounds in which there is a metallic Huoride or chloride 

 with a basic oxide of the same metal. 



The following specimens are representatives of these types : 



Fluorite— England. (Cat. No. 49603, U.S.N.M.) 



Cryolite— Erigtok, Arksut-fiord, Greenland. (Cat. No. 46271, U.S.N.M.) 



Pachnolite— Evigtok, Arksut-fiord, Greenland. (Cat. No. 17895, U.S.N.M.) 



Thomseuolite— Evigtok. Arksut-fiord, Greenland. (Cat. No. 81696, U.S.N.M.) 



Gearksutite- St. Peters Dome, Pikes Peak, Colorado. (Cat. No. 48222, U.S.N.M.) 



Halite — Lincoln County, Nevada. (Cat. No. 15475, U.S.N.M.) 



Cerargyrite— Chanarcillo, Chile. (Cat. No. 1.3018, U.S.N.M.) 



Carnaliite— Stassfurt, Germany. (Cat. No. 83908, U.S.N.M.) 



Tachhydrite- Stassfiirt, (iermany. CCat. No. 83912, U.S.N.M.) 



i'.romyrite- Broken Hill mine, New South Wales. (Cat. No. 51262, U.S.N.M.) 



Atacamite— Huasco, Chile. (Cat. No. 16956, U.S.N.M.) 



Sulphides, selenides, and tellurides. — The elements sulphur, selenium, 

 and tellurium bear a marked resemblance to each other, and present 

 close analogies in their properties, occurrence, and mode of combining 

 with other elements. The terms suli)hi(le, selenide, and telluride 

 include all those com])Ounds in which sulphur, selenium, or telliiriuni 

 NAT Mrs 97 42 



