768 



Lausfordite. 

 Zarutite. 



Remingtonite. 



Parisite. 



Kiscliitimite. 



Weibeyitc. 

 Bastniisite. 



Phosgenite. 



REPORT OF NATIONAL MUSEUM, 1897. 

 Group i — Coutinued. 



Mg,,(OH>.,(CO,):,.21H.20. Triclinic. 



Ni;,(0H)4C0,.4H,0. c?) 



C. I'LUO— AND CIII.OHOCAKBONATES. 



Group 1. 

 [(Ca,Ce)F2]Ce(C03)3. Hexagonal. 



[(Ce,La,Di)F]C03. Hexagonal (?). 



Group 2. 

 (PbCD.COs. Tetragonal. 



OXVGEN salts: class, — SILICATKS. 



The silicates, derivatives of the several silicic acids H4Si04, H28iO.-„ 

 H2Si07, H2Si05, and HjSisOa, or compounds of silicon oxide with other 

 oxides, constitute about nine tenths of the known crust of the earth 

 and more than one fourth of the known kinds of minerals. Isomorphic 

 combinations are the rule, and tlie class exhibits great diversitj^ of 

 composition. For example, the ratio of oxygen iu silica to that in com- 

 bined oxide may vary for monad and dyad elements, such as potassium 

 or calcium, between 2:4 and 4:1; and for silicates of triad elements, 

 such as aluminuui or iron, between L*:G and 12:3. Again, it is not 

 unusual to find a silicate containing both potassium and calcium, or 

 the oxides of iron and aluminum, or of calcium and aluminum, and 

 that not necessarily in atomic proportion. But although certain oxides 

 are capable of mutual replacement in any and all proportions, such as 

 the sesqnioxides of iron, aluminum, etc., or the monoxides of calcium, 

 magnesium, iron, manganese, sodium, lithium, etc.; and though a sili- 

 cate may contain at once a mixture of sesquioxides and monoxides in 

 combination with silica, the place of a monoxide is not taken by a ses- 

 qnioxide, nor that of a sesquioxide by a monoxide. 



Petalite. 



Ilydrocastorite. 

 Milaritc. 



Enstatite. 



Bronzite. 



Diaclasite. 



Bastito. 

 Hypersthene. 



Amblystegitc. 



Szaboite. 



Group 1. 



AlLi(8i,Oft)2. 



Al.Ca,KH(Si,0.-,)6. 

 Group :2. The Pyroxenes. 

 a. Orthorboiubic section. 

 MgSiO;,. 



(Fe,Mg)Si03. 



Monoclinic. 

 Hexagonal. 



