BRITISH ORES. 
75 
■Crystals, of which a magnificent specimen from Devonshire will 
be found in the central Case No. 31 ; but more frequently it is 
found in an earthy form, often investing galena, from whose 
decomposition it results. Among the oxidized lead ores will 
also be found some brilliant rhombic crystals of Anglesite or 
sulphate of lead, and of the fine blue mineral called Linarite, a 
sulphate of lead coloured by copper. The phosphate of lead 
termed Pyromorphite , and known to our miners as “green 
linnets,” is a mineral in which the phosphoric acid is frequently 
replaced to a greater or less extent by arseuic acid, thus passing 
into the species called Mimetite. In these minerals the 
phosphate and arsenate of lead are associated with plumbic 
chloride. 
The rare vandate of lead. Vanadinite, is related by form and 
composition to the phosphates and arsenates of lead, and these 
again to the phosphate of lime called apatite. 
Iron. 
Case 46 . — Iron pyrites, although containing nearly one half 
its weight of metal, is used not so much as a source of iron as of 
-sulphur, and is hence known as sulphur ore. In Cornwall, 
where it is by no means an uncommon constituent of copper 
veins, it passes under the name of mundie, whilst the coal 
miner, who constantly meets with impure varieties, recognises 
them as brasses. 
The name pyrites is derived from the Greek {pur, fire) because, 
as Pliny says, “ there was much fire in it.” Iron pyrites is 
essentially a bisulphide of iron, and is identical in chemical com- 
position with Marcasite, a mineral which, however, crystallises 
in totally distinct forms ; ordinary pyrites appearing in cubes, 
octahedrons, or certain hemihedral forms derived indirectly from 
the cube, whilst marcasite occurs in a series of prismatic forms, 
which have suggested the name of rhombic pyrites. It 
frequently appears in irregularly shaped nodules common in the 
chalk, and the crystals are often aggregated into groups, forming 
the variety called “ cockscomb pyrites.” 
The arsenical pyrites or Mispickel has already been noticed as 
n source of arsenic (p. 73), and the bronze-coloured magnetic 
pyrites or Pyrrhotine will be mentioned in the description of the 
foreign ores. 
Case 47 . — In this country Magnetic iron ore is comparatively 
unimportant, occurring only in very limited quantity. The 
peculiar pisolitic ore from Rosedale in Yorkshire is interesting 
from its occurrence, as a deposit of considerable extent, in the 
dogger at the base of the Inferior Oolite. 
Case 48 . — As the most important of the numerous localities 
in which the valuable Hoematite or red iron ore is found in this 
country, may be mentioned Ulverstone in North Lancashire, and 
Whitehaven in West Cumberland. The ore is highly prized for 
yielding a pig-iron well fitted for conversion into Bessemer 
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