Iron pyrite

“ The ore is found in a sort of chloritic slate and iron pyrites which follow the ledge all around. The ore itself is a fine-grained pyrite, with a grayish color, and it is well suited by its sulphur and low copper contents, as well as by its properties for heap roasting. In heap roasting, the ore is hand-broken by Chinamen into small lumps before being hoisted to the surface. From the landing on the surface it is run out on long tracks under sheds, dumped around a loose brick flue and on a few sticks of wood formed in the shape of a V, which runs to the flues to give a draught. ”

“ The effects of oxidation may be seen in the alteration of many kinds of rocks and in red and yellow colors of soils and subsoils.
Pyrite is a very hard mineral of a pale brass color, found in scattered crystals in many rocks, and is composed of iron and sulphur (iron sulphide) . Under the attack of the weather it takes up oxygen, forming iron sulphate (green vitriol) , a soluble compound, and insoluble hydrated iron oxide, which as a mineral is known as limonite. Several large masses of iron sulphide were placed some years ago on the lawn in front of the National Museum at Washington. ”

“ Two minerals commonly met with in earths used for brickmaking are pyrite and marcasite, both of which are of the same chemical composition, namely, iron disulphide. We may first consider them separately, for they are of great importance to the brickmaker.
Iron pyrite occurs as regular cubic crystals, or irregular streaks, or as nodules or lumps; in clay, the last-mentioned is its commonest form. It is a good petrifying medium, so that it is frequently associated with organic remains, as is exemplified in almost any47 yard where stiff clay is being worked. ”

“ The mineral is abundant in Canada, where the presence of about 5% of nickel makes it a valuable ore of this metal. Iron disulphide, FeS2, constitutes the minerals pyrite and marcasite (q.v.) ; copper pyrites is (Cu, Fe) S2. Pyrite may be prepared artificially by gently heating ferrous sulphide with sulphur, or as brassy octahedra and cubes by slowly heating an intimate mixture of ferric oxide, sulphur and sal-ammoniac. It is insoluble in dilute acids, but dissolves in nitric acid with separation of sulphur. ”

“ PYRITES, a term applied to iron disulphide when crystallized in the cubic system, but used also in a general sense to designate a group of metallic sulphides of which this mineral is the most characteristic example. When employed as a group-name the constituent species are distinguished by prefixes: thus the type is called iron pyrites, whilst other species are known as copper pyrites, arsenical pyrites, &c. ”

“ But numerous cases of shales are known to us where iron pyrites replaces the shells of ammonites or forms complete casts of bivalves, and has accumulated also in concretions and crystalline groups. Such pyrites is probably of secondary origin, or arose from the reducing action of decaying organic matter on ferrous sulphate in solution in the sea.
The oxidation of iron pyrites in shales gives rise to aluminium sulphates, such as alums. Sometimes sufficient heat is evolved during this oxidation to set on fire carbonaceous matter present in the rock. ”

“ Figure 23—Calcareous tufa from Pike County. In addition to the large visible pores there are numerous tiny ones.
Pyrite and Marcasite
The mineral pyrite consists of iron and sulfur as the compound iron sulfide (FeS2) and, because of its shiny, brassy yellow color, is sometimes called fool’s gold. Marcasite has the same composition as pyrite, but its crystals have a different shape and it is often lighter colored. Both minerals occur in various parts of the state; they are particularly prevalent in some coal seams, and when so occurring are in some cases called coal brasses or “sulfur.” ”

“ Arms and food do not, however, complete our list of serviceable gifts to the dead. Among implements of this nature must be reckoned divers kinds of fire-producers. Excavations have shown that flint and iron pyrites were occasionally concealed in round barrows, while, in the mounds of later periods, a piece of iron replaced the customary mineral nodule. These ignition agents, the forerunners of our “strike-a-lights” and tinder boxes, are found so late as the Saxon period. ”

“ Impurities.—The properties of iron and steel, like those of most of the metals, are profoundly influenced by the presence of small and sometimes extremely small quantities of certain impurities, of which the most important are phosphorus and sulphur, the former derived chiefly from apatite (phosphate of lime) and other minerals which accompany the iron ore itself, the latter from the pyrite found not only in most iron ores but in nearly all coal and coke. ”

“ Metals are not generally found in the ground in a pure state. For the most part they are combined with oxygen or sulphur. Such was the case with the two specimens which Cyrus Harding had brought back, one of magnetic iron, not carbonated, the other a pyrite, also called sulphuret of iron. It was, therefore the first, the oxide of iron, which they must reduce with coal, that is to say, get rid of the oxygen, to obtain it in a pure state. ”

“ Copper pyrites may be distinguished from it by its golden yellow colour, which is frequently iridescent, and by its inferior hardness; for it does not strike fire with steel, like the preceding persulphuret. There is no vein, stratum, or mass of metallic ore which does not contain some iron pyrites; and it is often the sole mineral that fills the veins in quartz. It sometimes contains gold, and at other times silver. ”

“ This mineral, an iron disulfide, is so often mistaken for gold that it is widely known by the nickname fool’s gold.
Except for their similar color and luster, pyrite and gold are really very different. When you rub pyrite across a streak plate, it leaves a black, a greenish-black, or a brownish-black streak, but the streak of gold is gold-colored. Pyrite is too hard for the average pocket knife to scratch, but a knife will scratch gold easily. Pyrite is brittle and readily breaks, but gold is malleable and flattens out when hit with a hammer. ”

“ One gram of iron pyrites yields about 11 grams of lead. One gram of copper pyrites, blende, fahlerz, or mispickel, yields 7 or 8 grams of lead, whilst 1 gram of antimonite will give 6, and 1 gram of galena only a little over 3 grams. It is evident that if an ore carries much of these sulphides, the quantity of lead reduced will be very much larger than that required for an assay. To counteract this effect nitre is added; 1 gram is added for each 4 grams of lead in excess of that required. ”

“ Ores of Iron.—Even though the earth seems to be a huge iron meteor with but a thin covering of rocks, the exasperating proneness of iron to oxidize explains readily why this metal is only rarely found native, except in the form of meteorites. They are four important iron ores, magnetite, haematite, limonite and siderite, and one of less but still considerable importance, pyrite or pyrites.
44. Magnetite, Fe3O4, contains 72.41% of iron. It crystallizes in the cubical system, often in beautiful octahedra and rhombic dodecahedra. It is black with a black streak. ”

“ All these yield their copper in solution on boiling with hydrochloric acid.
The sulphides are more abundant. Copper pyrites (or yellow ore) , erubescite (or purple ore) , and chalcocite (or grey ore) are the most important. Iron pyrites generally carries copper and is frequently associated with the above-mentioned minerals. These are all attacked by nitric acid. They nearly all contain a small quantity of organic matter, and frequently considerable quantities of lead, zinc, silver, gold, arsenic, bismuth, &c. ”

“ Analyses usually, however, show the presence of more iron, owing to the intimate admixture of iron-pyrites. Traces of gold, silver, selenium or thallium are sometimes present, and the mineral is sometimes worked as an ore of gold or silver. ”

“ It might perhaps have been, to some extent, advantageously enlarged; although, it is true, the author refers us to the particular minerals for individual instances; still it might have been well to have illustrated the general principles by a few well-chosen instances, e. g. how, by the blowpipe, galena is distinguished from sulphuret of antimony; carbonat of lead from sulphat of barytes, or carbonat of lime; garnet from titanium; plaster of Paris from soapstone, &c.; and, among trials in the moist way, how by nitric acid and ammonia, iron pyrites is distinguished from copper pyrites ”

“ Pyrite is the commonest form of iron sulphide, and occurs in rocks of all ages, from Archean to Recent. It is formed in nature by the action of soluble sulphides or sulphuretted hydrogen on soluble salts of iron, and also by the reduction of sulphate of iron by organic matter or other reducing agents. Manganese forms two23 sulphides, alabandite (MnS) and hauerite (MnS2) . Both minerals are very rare, and so unstable that they rapidly oxidize on exposure. Alabandite is the less rare form, and usually occurs as a subordinate constituent of certain metalliferous veins or allied deposits. ”

“ That is to say, you can scratch gold with a common knife. Now, iron pyrites is harder than steel, and therefore a knife will fail to scratch it. Gold and iron pyrites, therefore, need never be mistaken for each other by any man who has a piece of steel about him. Copper pyrites can be scratched with steel. But then there is another very familiar property of gold, by which, in this case, it can be distinguished. Gold is very malleable ”

“ Sometimes they have petrified into iron pyrites or copper compounds, shining like gold, and then they make very noble thunderbolts indeed, heavy as lead, and capable of doing profound mischief if properly directed. ”

“ But iron pyrites, blende, fluate of lime, quartz, and sometimes chlorite, or flucan, frequently prevail for many fathoms, occasionally mixed with portions of the country through which the vein passes, though frequently with but slight traces either of tin or copper. A vein is sometimes found to consist of little else than a bed of hard and unpromising iron pyrites, which occasions its being abandoned; in others are found the ores of tin or copper, sometimes both, intermingled with some, or even most of the foregoing substances ”

“ They have, however, at some points, a metallic appearance at the surface, they lie at right angles to the general direction of the veins of the country, go down vertically, and being associated abundantly with several varieties of iron pyrites, oxides of iron, fluor spar and quartz, and containing traces of copper and lead, will doubtless at no very distant day, be explored to a greater or less extent. There is not a single county west of the Blue Ridge, that does not contain in abundance rich iron ores. ”

“ Arsenic is a constituent of the minerals arsenical iron, arsenical pyrites or mispickel, tin-white cobalt or smaltite, arsenical nickel, realgar, orpiment, pharmacolite and cobalt bloom, whilst it is also met with in small quantities in nearly all specimens of iron pyrites. ”

“ Iron pyrites dispersed through the mass is not uncommon, and when scratched the smell of sulphuretted hydrogen is rendered sensible: it burns very white, a circumstance which shows that the colouring matter, being volatile, is of an animal or vegetable origin. ”

“ Where beds of common iron pyrites occur, the iron sulphide is converted into sulphate by exposure to the oxidising influence of the air. The result is an acid sulphate of iron, which is leached out and neutralised by addition of more iron in the form of scrap. The neutral sulphate is crystallised out of the liquor, and calcined in a muffle furnace, the shade of the ultimate product being governed by the degree or duration of the roasting. ”

“ The washed sample is then fused in the usual way to determine the proportion of sulphur existing as iron pyrites. The distinction between sulphur present as sulphate and sulphide is of importance in the examination of coals intended for iron smelting, as the sulphates of the earthy metals are reduced by the gases of the furnace to sulphides, which pass into the slag without affecting the quality of the iron produced, while the sulphur of the metallic sulphides in the ash acts prejudicially upon the metal. ”

“ Rock Salt (pseudomorphs) , Aust; Steatite, Tortworth; Talc, Tortworth; Vivianite, near Clifton.
Pyle Hill, near Clifton, is a well-known locality for Celestine. At Garden Cliff, near Westbury-on-Severn, the “bone bed” is well exposed, and in this bed occurs plenty of iron pyrites; and in the shales, as might be expected, crystals of selenite occur.
Leicestershire.—Gold occurs in the quartz veins round Pedlar Tor, Charnwood Forest. Garnets occur in “gneiss” at Brazil Wood (Mr. W. J. Harrison) . Copper pyrites, Molybdenum, Mount Sorrel and Breedon. ”

“ I come, therefore, to the conclusion, that a certain proportion of these instruments were in use, not for scraping hides like the others, but for scraping iron pyrites, and not improbably, in later days, even iron or steel for procuring fire. Were they used for such a purpose we can readily understand why they should so often present a bruising of the edge and an irregularity of form. We can also find a means of accounting for their great abundance. ”

“ Associated with the pyrites in small quantities are various substances, some of which, becoming volatilised when the ore is burnt, enter the chambers with the mixed gases, and thus find their entrance into the acid, whilst others remain behind in the iron residue of impure ferric oxide, left on the hearth of the furnace after roasting. ”