THE MINERALS OF CHILE. 101 



Valdivia; in the geodes, marine shells (Turritella) are frequently found of very modern alluvial 

 formation, like that in which the lignites of Conception and Colcura are found. Breithaupt 

 called a prismatic crystalline variety of this mineral from Chile Chileite, without, however, 

 any just grounds of separating it from the gothite proper. The analysis of the Chileite, as 

 given by Breithaupt, is — 



Peroxide of iron - - - - - -83.5 



Water -----_.. 10.3 



Copper --------1.9 



Silica -4.3 



100.0 

 Formula, ffe fl. 

 Pyrites. — The different varieties of iron pyrites are found in all parts of Chile. They some- 

 times contain an appreciable amount of gold. 



Coquimbite — fFhite Copperas. — The Tierra Amarilla, near Copiapo, is a seam of pyrites that 

 crosses compact feldspathic rocks, and from its decomposition several minerals result. The one 

 in question occurs in regular hexagonal plates of a yellowish- white color and pearly lustre. 

 It has a strong, astringent taste, and is quite soluble in water. It is a neutral sulphate of iron, 

 as shown by Kose's analysis — ■ 



Peroxide of iron ------ 24.11 



Sulphuric acid ------ 43.55 



Alumina ___-__- 0.92 

 Lime - - - - -- - - 0.73 



Magnesia ------- 0.32 



Silica -------- 0.31 



Water - 30.10 



100.04 

 ItB formula is 3P S^ 4- 9 fl. 

 Copiapite — Yellow Copperas. — This occurs associated with the last, and is most commonly 

 found in fibrous masses, of a beautiful silky lustre when the fracture is fresh; it, however, soon 

 becomes of a rusty color. It is not so soluble as the last, and is a basic salt. 



Its specific gravity is 1.84. On analysis it furnished — 



1. 2. 



Sulphuric acid _ - _ - 30.25 30.42 



Peroxide of iron - - - - 31.75 30.98 

 Water ------ 38.20 



TT T n 1 ,. Ki I not estimated. 



Undissolved - - - - -0.54) 



100.74 



The analyses correspond to the formula 3Pe S^ 4- 11 fi. 

 Arseniuret of Iron. — This mineral is of metallic lustre, of a silver-white color. Specific gravity, 

 Y.3. It is found in several of the silver mines of Chile, especially those of Carriso, where it is 

 accompanied by mispickel, iron pyrites, blende, native antimony, ruby silver, and native silver. 

 A specimen analyzed by M. Domeyko furnished — 



Arsenic -------- 70.3 



Iron 27.6 



Sulphur 1.1 



Silver -------- .2 ■ 



99.2 

 The formula is Fe As. ==^ 



