FOREIGN ORES. 
79 
stratum lying at the base of the Zechstein, or magnesian lime- 
stone, extends uninterruptedly over a very wide area, and in 
spite of its thinness and its poverty of ore is successfully worked 
at several points, especially at Mansfeld in Prussian Saxony. 
Occasionally the cupreous schist contains the fossil remains of 
Permian fish, and a fine specimen of one of the most common 
species of Palceoniscus is here exhibited. The metallurgical 
treatment of the Kupferschiefer will be subsequently noticed, 
(See p. 93.) 
Iron. 
Case 18 , — The series of iron ores commences with several 
specimens of Magnetite, or magnetic iron ore, from the hills of 
Blagodat in the North Ural ; but the most interesting samples 
of this mineral are those from the famous iron mines of Sweden. 
Some of the best iron is obtained from the Dannemora mines in 
Upsala Lin, of which large quantities are employed at Sheffield, 
and other places for making steel. 
The series of iron ores is interrupted by a small number of : 
titanium minerals, among which may be noticed the unusually 
large crystals of Rutile from the United States ; the splendid 
crystals of Arkansite, a variety of Brookite from Arkansas, 
United States ; and the little square octahedra of Anatase from 
the Grisons. Some fine crystals of Sphene, a silicate of calcium 
and titanium, are also worthy of notice. Geikielite is a titanate 
of magnesium, from Ceylon, recently described by Mr. Dick. 
Returning to the iron -producing minerals, we find several 
shelves occupied by examples of the different varieties of 
Hcematite or red iron ore. Among these the eye will be 
especially attracted by the brilliant lustre, and in many cases by- 
the iridescent tarnish, of the crystallised variety called specular 1 
iron ore, of which the Isle of Elba has contributed some 
beautiful examples. The Elban specular ore, celebrated from 
remote antiquity, occurs in enormous deposits on the eastern 
side of the island, where it has long been worked by large open 
excavations, principally at Rio. Even more brilliant than the 
Elban specimens are the splendid plates of specular ore from 
Brazil. 
Case 19 . — Limonite, brown iron ore or hydrous peroxide of 
iron, occasionally called “ brown hcematite,” is a very abundant 
and widely- diffused mineral, resulting frequently from the 
decomposition of other iron ores, and often associated with the 
ores of manganese. The fine stalactitic and botryoidal forms of 
the Russian specimens, and the fibrous structure of many of the 
German samples, sufficiently show the characters of the purer 
varieties ; whilst the friable earthy forms passing into ochre are 
illustrated by examples from various localities. The pure 
crystallised hydrous per-oxide of iron, of definite composition, 
has been separated as a distinct species under the name of 
Gothite. 
