125 



A curious earthy mineral, consisting o£ hydrated alumina Bauxite. 

 and, in most cases, a varying amount of ferric and titanic oxides, 

 silica, &c. In its purest form it usually has a pisolitic structure, 

 well shown by some of the Georgia ore (3558). The name is 

 derived from the French district of Baux, where deposits occur. 



4154, Erance ; pisolitic red variety. 



7534, Antrim ; white variety. 



Fluorldeof aluminiumand sodium. Cryolite has a characteristic Cryolite, 

 icy appearance, from which its name is derived. It is one of the 

 very few minerals that will melt in a candle flame. It occurs in 

 quantity in Grreenland onlj'-, where it is extensively quarried. 



3347, Greenland. 



3214, Pikes Peak, Colorado. 



6847, Mellite (hydrous mellate of alumina), Eussia, 



TELLURIUM. Case 92. 



Tellurium is a rare element, closely allied to sulphur in its 



chemical characters. It is very exceptionally found as native 



tellurium, hut more usually occurs combined with bismuth, gold, 



and silver. Tellurium is of special interest, because of its 



frequent association with gold. 



A constant characteristic of tellurides is their softness; they are all 

 readily scratched with the point of a knife, and some with the 

 fingernail. In appearance they are all metalHc* 



A number of ores from" Cripple Creek, Colorado, are placed 

 here for convenience (see page 105). 



3444, 3464, Colorado. Native 



tellurium. 

 Silver telluride. Hessite. 



6464, Tuolomne County, Colorado, 



Tellurides of gold and silver. 6463, Tuolomne County, Petzite and 

 Colorado : calaverite, with much free gold. 



* A simple chemical test for a telluride is to put a speck of the mineral with a few drops of 

 strong- sulphuric acid in a porcelain dish — a saucer will do very well— and gently warm it over 

 a flame, taking- care that the heat is not great enough to cause fumes to come off. If tellurium 

 be present in any quantitj', oarmine-coloured streaks will appear in the liquid tailing- off 

 from the speck. 



