64 
ZINC. 
Case D. — Zinc ores, New Jersey and Wisconsin. 
The ores from New Jersey are unique. They consist chiefly 
of the oxides franklinite and zincite and the silicate willemite. 
This is a combination of ores that occurs nowhere else. 
Case E. — ^Zinc ores of Missouri. The zinc-bearing minerals 
of these ores are chiefly the black, resinous sulphide, sphalerite 
and the white csivhondiie, smithsonite. 
Case F. — Zinc ores, northwest Arkansas. The zinc is largely 
in the form of the white carbonate, smithsonite. 
Case 6. — Zinc ores, Great Britain; chiefly sphalerite. Though 
the sphalerite varies much in color in these specimens, it may al- 
ways be distinguished from the associated minerals by its resinous 
appearance. The very dark specimens are the “black jack” of the 
Cornish miners. 
Case 7. — Zinc ores from Spain and Germany. Note the 
parallel arrangement of the minerals in the latter, this being a 
characteristic of vein deposits. The chief mineral, sphalerite, is 
associated with quartz, galena, pyrites, etc. 
Cases 8, 9 and 10. — ^Zinc ores chiefly from Laurium, Greece 
and New South Wales. The former have long been famous for 
their varieties of color and richness of luster, making them very 
attractive to the eye. They are made up chiefly of the carbonate, 
smithsonite. 
Specimens illustrating the process of extraction of zinc, are 
shown in Case lo. 
TIN. 
Case 11. — Tin ore from South Dakota. The tin is in the form 
of cassiterite, a black oxide which can be seen scattered through 
the granite. This is the universal ore of tin, containing when pure 
about 78 per cent, of the metal. Some specimens of stream tin 
are also shown. This is formed by disintegration of the rocks con- 
taining the ore, and removal of the lighter minerals by running 
water. The cassiterite being very heavy stays behind and is 
found in the bed of the stream. 
Case 12. — Tin ore, New South Wales. 
Case 13. — Tin ore from the famous Cornwall Mines of Great 
Britain, which have been in operation many centuries. 
