BRITISH AND FOREIGN ORES. 
77 
less extent the carbonate of iron. Moreover this carbonate of 
iron is frequently associated with impurities which interfere 
with its crystallisation, and give rise to the dark-coloured 
massive varieties called clay -ironstones. These impure car- 
bonates — which are so profusely distributed throughout our 
coal-measures, partly as regular seams of variable thickness, and 
partly as nodular concretions — constitute the ore which, in this 
country formerly yielded by far the largest amount of our iron 
— a fact by itself a sufficient apology for the rather large 
amount of space devoted to the display of these ores, confessedly 
somewhat unattractive in appearance. But the exhibition of 
a complete series is the more desirable in an institution of a 
practical character, since the ores, possessing neither crystalline 
form nor definite chemical composition, are not entitled to take 
rank as true mineralogical species, and would therefore find no 
place in a purely scientific collection. 
The extensive series of clay-ironstones commences, with a 
number of specimens illustrating the characters of the nodular 
forms, and the minerals which these nodules frequently contain. 
The lower part of Case 50 and the whole of the six following 
cases are occupied by the systematic collection of ironstones, 
arranged geographically in the following order : South Wales, 
North Wales, Shropshire, South Staffordshire, Warwickshire, 
North Staffordshire, Yorkshire, Derbyshire, and the Northern 
Counties. 
Intercalated with these argillaceous carbonates of iron are a 
few samples of the carbonaceous ironstone, well known as black 
band. This ore, which was discovered in 1801 by Mr. Mushet, 
and is hence frequently called Mushet stone, is largely used in 
the manufacture of Scotch iron. 
FOREIGN ORES. Wall Cases 15 to 23. 
Copper. 
Case 15. — Among the specimens of Native copper which head 
the series of copper-bearing minerals, attention may be especially 
directed to the fine samples from the remarkable deposits around 
Lake Superior. There exists abundant evidence to show that 
these deposits were worked at a very remote period ; and one of 
the stone hammers used by the primitive miners will be found 
in Table-case 23. All tradition, however, of these early workings 
had been lost, and the existence of the metal became known 
only by the occurrence of masses of copper on the shores of the 
lake. In 1845 operations were commenced at the Cliff Mine, 
and these were rapidly followed by other workings. T^he copper- 
lands on the south side of the lake consist of Cambrian, or Pre- 
cambrian (Keweenawan), sandstones and conglomerates, with a 
