kansome.] ORE MINERALS. 83 
Argentite.— Silver sulphide (Ag 2 S), containing 87.1 per cent of sil- 
ver. Isometric. Blackish lead-graj 7 . Hardness, 2 to 2.5.^ Sectile. 
Specific gravity, 7.3; 
This valuable ore of silver, which is readily distinguished by the 
ease with which it can be cut with a knife without breaking or splin- 
tering, is not abundant in the Silverton quadrangle. It was distinctly 
recognized only at the Ridgway mine, where, curiously enough, it is 
called " brittle silver." Here it constitutes the richest ore, and is evi- 
dently one of the most recently formed of all the ore minerals, as it 
occurs characteristically in vugs, incrusting or filling the interstices 
between the quartz crystals. It probably occurs also in the Gold Nug- 
get and other prospects in Maggie Gulch, and is said to have consti- 
tuted a Large part of the rich ore formerly extracted from the Polar 
Star mine, on Engineer Mountain, and from the Palmetto mine, in 
American Flats. 
Molybdenite. — Molybdenum disulphide (MoS 2 ). Probably hexagonal. 
Occurs in scales, with eminent basal cleavage, or compact. Laminae 
flexible, but not elastic. Lead-gray. Leaves a bluish-gray mark on 
paper. Feel, greasy. Hardness, 1 to 1.5. 
This mineral occurs in the Sunnyside Extension mine, where it has 
been mistaken for graphite. Here it frequently contains free gold. 
It lias not been recognized elsewhere within the quadrangle. 
Hematitt (specularite). — Ferric oxide (Fe 2 3 ). Rhombohedral. 
Lamellar or in thin scales. Color, steel-gray or iron-black. Streak, 
cherry-red or reddish-brown. Hardness, 5.5-G.5, but often apparently 
much softer on account of its scaly structure. Specific gravit}^, 5.2. 
The variety of hematite known as specular iron is frequently met 
with in small quantities in the lodes of the Silverton quadrangle. It 
occurs, for example, in the Crown Point lode on Silverton Moun- 
tain, in the Little Giant lode (on the dump), in the Neigold claims on 
Galena Mountain, and in the Daniel Webster x>rospect in Maggie 
Gulch. In all cases observed it is a vein mineral inclosed in quartz. 
It is of no economic importance, but is frequently mistaken for more 
valuable minerals — in one case for "brittle silver." It is easily recog- 
nized by its scaly structure, brittleness, and red color when crushed. 
Sulphobismuthites. — These include cosalite (2PbS.Bi 2 S 3 ), galeno- 
Tnsmuthite (PbS.Li,S,), alaskaite ((PbAg 2 )S.Bi 2 S 3 ), beegerite (6Pb- 
S.Bi 2 S 3 ), kobellite (2PbS.(Bi,Sb),S :; ), and possibly other species. 
Sulphobismuthites of lead, carrying usually considerable silver and 
sometimes a little copper, are of frequent occurrence, particularly in 
the northern half of the quadrangle. As most of the above-named 
minerals resemble one another very closely in physical properties and 
as a rule occur massive, their specific identification is impossible 
without a quantitative chemical analysis in each case. Nor is this 
method often available, for the association of these sulphobismuthites 
with other ore minerals is usually such that pure material suitable 
