272 
Notices of Boohs, 
[April, 
Annual Report of the United States Geological and Geographical 
Survey of the Territories, being a Report of Progress of the 
Exploration for the Year 1873. By F. V. Hayden, United 
States Geologist. Washington : Government Printing 
Office. 
This volume is especially devoted to Colorado, a region of great 
interest to the geologist. Amongst its valuable features we in- 
stance a catalogue of the minerals of Colorado, with their 
localities. Amongst these a prominent place belongs to certain 
tellurium compounds. These rare minerals occur at Red Cloud 
and Cold Spring, on both sides of a porphyry dyke, 50 feet in 
thickness, intersecting the granite, and striking about norch-east. 
The tellurides of this region seem to show a greater variety of 
composition than those of any other locality hitherto known. 
Native tellurium occurs both massive and in small hexagonal 
crystals, with perfedt lateral cleavage, forming columnar masses 
in white quartz. In hardness it ranges from 2 to 2*5. Its 
specific gravity is 5*802. It is lamellar in structure ; tin- 
white to light steel-grey in colour; lustre splendent ; streak sub- 
metallic, light grey to grey. It is less pure than the tellurium of 
Transylvania, containing only 90*85 per cent of tellurium, along 
with selenium, iron, and bismuth, and traces of gold and silver. 
Another telluride, occurring in the Red Cloud and Cold Spring 
mines, has received the name of Henryite. It is found in im- 
perfect crystals, with good cubical cleavage, in thin threads, or 
in irregular foliated masses. Its hardness ranges from 2 to 2*5. 
Its specific gravity is 8*5253; its lustre metallic, splendent; 
colour bright silver-grey to steel-grey, but after exposure to the 
atmosphere for a short time it becomes a pale bright yellow. 
The streak is metallic, grey to silvery; it is opaque, brittle, 
partly malleable and sedtile. Its composition is — 
Lead 
53 #I 9 
Iron 
5'°5 
Silver 
0*31 
Gold 
trace 
Tellurium (by difference) 
4 1 ‘45 
100*00 
which leads to the formula 3PbTe-f-FeTe, a small portion of the 
lead being replaced by silver. In its physical characters this 
mineral approaches Altaite, which contains 60 per cent of lead, 
and no iron. Schirmerite, another new mineral, is found in thin 
threads and foliated masses. Its cleavage is perfect ; hardness, 
1 to 1*5 ; lustre metallic, splendent; streak dark grey to black; 
colour between light lead-grey and steel-blue ; opaque, partly 
malleable and sectile ; flexible and thin scales. It contains 
18*82 per cent of gold, and 28*60 of silver. The residue com- 
