94. DESCRIPTIONS OF MINERALS. 
Tron occurs in the state of sulphide (very common, but not 
useful as an ore of iron), of arsenide, sulph-arsenide, oxide (the 
common ores of iron), carbonate (useful ore), sulphate, arsen- 
ate, phosphate, silicate. e 
Manganese occurs in the state of sulphide (rare), arsenide 
(rare), oxide (the common ores), carbonate, sulphate, phosphate, 
silicate. 
I. MINERALS CONSISTING OF THE ACIDIC 
ELEMENTS. 
Oxygen might properly be included in this section, since it 
occurs native in the atmosphere mixed with nitrogen, consti- 
tuting 21 per cent. of it. But this mention of it is all that is 
necessary. The ternary compounds, in which, as in sulphuric 
acid, hydrogen is the basic element, are here included. Chlor- 
ine, bromine, and iodine do not occur native, and neither do their 
oxides, nor any compounds with acidic elements, and hence these 
elements are not represented under this division. The same is 
true of selenium and chromium of the sulphur group, and of 
vanadium, tantalum, and columbium of the arsenic group. 
I. SULPHUR GROUP. 
Native Sulphur. 
Trimetric.—In acute octahedrons, and secondaries to this 
form, with imperfect octahedral cleavage. 1/1 (in same pyra- 

mid) = 106° 25’ and 85°-07%5 LAI (over base) ==9143- eae 
Also massive. 
Color and streak sulphur-yellow, sometimes orange-yellow. 
