73 
ores from New Granada are more quartzose than most of those ex- 
hibited, and in this respect resemble those of California. 
Case 6. — Gold ores, Great Britain and Australia. The col- 
lection from the New Morgan Mine, Dolgelly, Wales, is worthy of 
special attention both on account of its completeness and on 
account of the character of the ore. The gold is nearly all free, 
and much of it is visible to the eye. Specimens of ore from vari- 
ous parts of the mine are shown, also specimens of the country 
rock. 
Case B. — Collection of nearly all the known alloys of gold 
and silver with copper, tin, zinc, lead, arsenic, and other metals. 
Collection illustrating methods of saving gold and silver practiced 
by Messrs. Tiffany & Co., New York. Here are shown wash 
water, concentrates from an exhaust blower that collects the dust 
of the shops, pieces of flooring of the shops, and shoes worn by 
workmen, and besideYach of these are placed buttons of gold and 
silver obtained from articles of size similar to those shown. 
Case C. — Large specimens of gold ores, Colorado. 
SILVER. 
Case 7, Front. — Type specimens of silver-bearing min- 
erals. These are, in the order of their richness: 7 iative, or u ire 
silver ; ar^s^entite^ 87 per cent, silver; cerargyrite^ 75 per cent, sil- 
ver; pyrargyritey 65 per cent, silver; proustite, 65 per cent, silver; 
stephanitey 68 per cent, silver. Galena and cerussite may also be re- 
garded as ores of silver, for, though they contain but small percent- 
ages of silver, they are so abundant as to constitute very important 
ores. With these should be mentioned, Tetrahedritey which may 
contain as high as 17 per cent, of silver. There are a number of 
rarer silver-bearing minerals. 
Cases 8, E), and E.— Silver ores, Colorado. The silver 
ores of Colorado pass by insensible gradation into silver-lead ores, 
so that these two classes should be studied in connection. Note the 
great variety of the Leadville ores. On the upper shelf of Case 8 
there is a small quartz vein in which many particles of native silver 
may be seen. 
