56 
The colour varies between reddish yellow and brass 
yellow, it is sometimes however converted into brown-red, 
while a part of the mineral is decomposed and changed 
into a hydrous oxide of iron. This variety has been 
called hepatic pyrites (from liver). The metallic 
lustre is remarkable at least in a fresh fracture, the hard¬ 
ness = 6*0—6*5, the specific gravity 4*9—5*0. The con- 
rr 
stituents are bi-sulphuret of iron = Fe, with equivalent of 
iron (45’74) and 2 eq. of sulphur (54*26). When heated 
in the retort some of the sulphur is sublimed. On the 
matrass vapours of sulphureous acid are given off, and there 
remains at last red oxide of iron. It is dissolved with 
separation of sulphur by nitric acid. 
Pyrites is found in all formations, partly in veins, 
partly in layers or beds, and partly disseminated. The 
finest crystals are found at Traversella in Piedmont, where 
the pieces figured 2—5 were obtained, also in the island 
of Elba, at Wittich in the Schwarzwald, in England, Nor¬ 
way, Sweden, etc. Pyrites containing silver is found in 
Hungary, and an auriferous or gold-bearing variety occurs 
in the neighbourhood of the Urals and of the Alps. 
When it occurs in abundance it is used for the manu¬ 
facture of sulphur, and sulphuric acid, sulphate of iron, 
etc., it is also used as a flux in smelting many silver ores. 
Fig. 9—12.— Marcasite, Spear-Pyrites, White 
Iron Pyrites. 
Is distinguished from the foregoing by the form of 
its crystals, which is primarily a right rhombic prism, and 
by its colour, which is more inclined to a steel-grey. Be¬ 
sides the primary form, however, truncations of the acute 
angles frequently occur, as Fig. 10, also aggregations of 
small rhombic tables, like Fig. 9, twin-combinations of 
from 3—6 segments of crystals, similar to Fig. 11, oblong 
octahedrons arising from truncation of the angles, with 
hemihedral bevelling in part, like Fig. 12, also radiated 
and stem-like masses, nodules and kidneys, etc., which can 
very easily be separated so as to form small needles of 
sulphate of iron. Friable and hard like the preceding ore, 
the specific gravity generally somewhat smaller ( = 4*6— 
4*8). The constituents and the behaviour before the blow¬ 
pipe as in pyrites; the two minerals, therefore, offer a re¬ 
markable example of dimorphism. 
It occurs principally in veins and in stratified rocks, 
but particularly in the neighbourhood of the stone-coal, 
brown-coal, and in bituminous schists, which, on breaking 
down, yield alum and sulphate of iron, and are therefore 
called alum schists. Many of these pyrites contain arsenic, 
others contain traces of copper, silver, or gold; the first 
are usually remarkable for their bright yellow colour. 
Fig. 13—16.— Magnetite, Magnetic Iron Ore. 
Crystallises in regular octahedrons, as in Plate I., Fig. 
22, which sometimes appear variously distorted or tabular 
by extension of a single pair of surfaces, as Fig. 14, or they 
form twins, as in Fig. 13. Truncations of the edges and 
angles also occur, and combinations of the octahedron with 
the rhombic dodecahedron and cube, or simple dodecahe¬ 
drons, which then exhibit a situation corresponding to the 
edges of the octahedron, as in Fig. 16. These beautiful 
crystals are from Traversella in Piedmont, and Figs. 13 and 
14 from Pfitsch in the Tyrol. Granular, dense, and some¬ 
times also perfectly compact masses are more frequent. 
The colour is iron-black, sometimes externally inclined to 
brown, the streak is greyish-black, and the lustre slightly 
metallic; the fracture is conchoidal to uneven, the friability 
considerable, the hardness = 5’5—6'5, so that it gives out 
sparks with steel, and the specific gravity 5*09. It is 
attracted by the magnet under all circumstances, and thus 
may be readily distinguished from franklinite and the 
chromic ironstone, as well as from hematite. The consti¬ 
tuents are protoxide and peroxide of iron = Fe Fe, con¬ 
sisting of 71*87 of iron, and 28*22 of oxygen. Infusible on 
the matrass, giving a red oxide in the outer flame ; when 
finely powdered it melts in borax to a grass-green bead, 
which, in the inner flame, becomes light-green, and in the 
outer an olive-green passing into yellow. Soluble in heated 
acids. The compact magnetic iron sometimes contains 
titanium, and the compact magnetic ironstone is frequently 
of itself magnetic, so that by its aid artificial magnets may 
be made. The finest crystals are found in the Zillerthal, 
and in the Pfitschthal in the Tyrol, at Traversella in Pied¬ 
mont, in Saxony, Thuringia, Moravia, etc.; the finest 
beds of compact ore are found at Arendal in Norway, 
Dannemora in Sweden, also in Moravia, Persia, India, etc. 
One of the most valuable of iron ores, which, where- 
ever it occurs in considerable quantity, is smelted for iron, 
and yields the best bar-iron and steel. The best English 
steel is manufactured from such Swedish or Norwegian iron. 
The octahedral titanic iron , iserine , etc., externally per¬ 
fectly similar to the preceding, is a magnetic iron contain¬ 
ing more or less titania; w r hen finely powdered and melted 
with salt of phosphorus, in the inner flame it yields a 
red glass, which becomes violet, and finally colourless, on 
the addition of some tin; it is found in small octahedral 
grains at the Iserwiese in Bohemia, and in the form of 
sand in many rivers of Auvergne and other volcanic 
districts. 
Fig. 17—21.— Hematite, Specular Iron, 
Red Iron Ore. 
Is found-crystallised, foliated, fibrous, scaly, earthy, and 
compact. The crystals exhibit a strong metallic lustre, 
and a steel-grey colour. The primary form is a rhombo- 
hedron, of which, however, the vertex is usually truncated, 
as in Fig. 17, so that the rhombohedral octahedron pre¬ 
dominates. Combinations of several rhombohedrons with 
the scalenohedron, like Fig. 18, are more frequent, or 
hexagonal double pyramids, in the form of a table, like 
Fig. 19, or groups of hexagonal tables, like Fig. 20; the 
two latter forms are found especially at St. Gothard, Fig. 
17 at Vesuvius, and Fig. 18 in the island of Elba. The 
streak is a browm-red to a crimson, the fracture uneven to 
conchoidal, the hardness 5*5—6 - 5; all the crystallised and 
compact varieties give sparks with the steel. The specific 
gravity is = 5-0—5‘3. It is readily distinguished from 
magnetic iron by its stronger lustre, by the red streak and 
the different form of the crystals, and it is not attracted 
by the magnet. There are, however, pseudomorphs of 
the form of magnetic iron, the so-called marthite , which 
