HANDBOOK FOR THE DEPARTMENT OP GEOLOGY. 533 



The sulphides although of minor importance as rock masses are of 

 the very greatest importance as ores, in which collections the visitor 

 will find a very full series. 



Sulphates : 



Anhydrite. Isere, France, 38197; Boisset, France, (with gypsum) 382L4 ; Vol- 

 pino, Bergamo, Italy, 36733 ; La Graz, Mt. Blanc, 36114 ; Nova Scotia, 36102. 

 Gypsum : 



Graud Rapids, Michigan, 35590 ; North Ogdeu Canon, Colorado, 3U771 ; Windsor, 

 Nova Scotia, 13690 and 37624 ; State of Pueblo, Mexico (Satin Spar), 37815 5 

 Argentine Republic, 35531 ; Galica, Austria, 38817. 

 Barite or sulphate of barium. Vangueray, France, 38198. Ahmite, or sulphate of 

 aluminum and potash. Huugary, 36034. 



(5) Phosphates. — The mineral apatite, a phosphate of lime as already 

 noted is a common accessory in the form of small crystals in crystalline 

 rocks of all ages. It also sometimes occurs in the form of crystalline 

 granular aggregates constituting true rock masses associated mainly 

 with the older rocks of the earth's crust. It is therefore given a limited 

 space here. The following localities are represented : Apatite mines of 

 Bamle, Norway, 18873 ; Burgess, Ontario, Canada, 3G128 ; France, 

 38143. (See also mineral fertilizers in economic series.) 



(6) Chlorides. — Sodium chloride, or common salt is one of the most 

 common constituents of the earth's crust. From an economic stand- 

 point it is also a most important constituent. It occurs in greater or 

 less abundance in all natural waters, and as a product of evapora- 

 tion of aucient seas and lakes it occurs in beds of varying extent and 

 thickness among rocks of all ages wherever suitable circumstances have 

 existed for their formation and preservation. Salt beds from upwards 

 of a few inches to 30 feet in thickness occur in New York State and 

 Canada, while others abound in Pennsylvania, Virginia, Ohio, Michi- 

 gan, and Louisiana. There are also numerous surface deposits of great 

 extent in the arid regions of the West. The chlorides are here illus- 

 trated only by specimens from Lincoln County, Nevada (15501) ; New 

 Iberia, Louisiana (38461). 



(7) The hydrocarbon compounds.— Here are brought together a 

 small series of rocks consisting as do the mineral coals of carbon in 

 combination with hydrogen and sometimes oxygen, and which are re- 

 garded as products of distillation or chemical alteration of buried 

 organic matter, both plant and animal. Many compounds of the series 

 are of a gaseous nature (natural gas, etc.,) and hence not applicable for 

 exhibition purposes. Several members of this group are of great im- 

 portance from an economic standpoint and a more complete display is 

 given in the room devoted to economic geology (southwest court). 



Petroleum is a mixture of natural hydrocarbons, liquid at ordinary 

 temperatures and with a specific gravity somewhat less than that of 

 water. In color it varies from nearly colorless through greenish to 

 black. (See color series in southwest court.) But two samples are here 



