Pyrite

“ Pyrite In Geneva and in the neighboring regions great virtues are ascribed to a cut and facetted iron (pyrite) , very hard, susceptible of a high polish and of resplendent lustre. This is cut to resemble the rose or brilliant form of diamond, and is set in rings, buckles, and other ornaments. In appearance it resembles polished steel and is called pierre de santé, or “health-stone,” for it is believed to grow pale when the health of the wearer is about to fail. [309] This substance is known as marcasite and is a bisulphide of iron. ”

“ The sulphide of iron, pyrite, occurs in many crystalline rocks; but, owing to the difficulty of separating the iron and sulphur, is not used as an ore of iron. The mineral much resembles in external appearance a yellow ore of copper, called chalcopyrite, from which it may be distinguished in that it will strike fire with steel. A specimen of pyrites containing large crystals is an interesting subject of study. ”

“ 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. ”

“ 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. ”

“ Auriferous pyrite which occurs in auriferous countries contains certain quantities of gold, sometimes worth winning, and was known as King of the Pyrites. The action of water and air makes it troublesome in coal-mining districts. ”

“ 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 is a mineral of very wide distribution, occurring under varied conditions and probably originating in various ways. It is common in. mineral-Veins, usually associated with quartz, and is often known to miners as “ mundic.” It occurs crystallized, commonly in cubes, in schistose and slaty rocks, and less abundantly in the younger sedimentary deposits. In coal it not infrequently forms bands and nodules known as “brasses, 'f and may also be finely disseminated through the coal as “black pyrites”; but much of the so-called pyrites of coal is really marcasite. ”

“ 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. ”

“ Many fossils are mineralized with pyrites, which has evidently been reduced by the action of decomposing organic matter on a solution of ferrous sulphate, or perhaps less directly on ferrous carbonate dissolved in water containing carbonic acid, in the presence of certain sulphates. A similar action probably explains the origin of pyrites and marcasite in coal and lignite, in clay and shales, and in limestone like chalk. ”

“ 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. ”

“ It occurs in nature as the mineral melanterite, either crystalline or fibrous, but usually massive; it appears to have been formed by the oxidation of pyrite or marcasite. It is manufactured by piling pyrites in heaps and exposing to atmospheric oxidation, the ferrous sulphate thus formed being dissolved in water, and the solution run into tanks, where any sulphuric acid which may be formed is decomposed by adding scrap iron. By evaporation the green vitriol is obtained as large crystals. ”

“ It is a common and very widely disseminated mineral in rocks of all kinds and ages, but especially in metamorphic rocks as veins, and banded or lenslike deposits. Most igneous rocks contain small scattering grains of pyrite. Many deposits of commercial value are known. Great quantities are burned for the manufacture of sulphuric acid (“oil of vitriol”) which is one of the most important of all chemicals.
Pyroxene Group. Along with quartz and feldspars, the pyroxenes rank among the most common of all minerals. (See Figure 74k.) Composition, very similar to amphibole (see above) . ”

“ 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. ”

“ It is the iron and copper pyrites that are everywhere mingled with the ore, and which, in many places, are found in the form of regular and beautiful crystals that send out from their facets flashes of light that almost rival the fire and splendor of precious stones. ”

“ 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. ”

“ The pyrites cinders from sulphuric acid works afford an abundance of oxide of iron. When the pyrites has contained no copper, the cinders merely require grinding and levigating, the iron being present as oxide. But when the pyriteshas been treated for the recovery of the copper, by a second roasting with salt, the liquors contain the iron as chloride and sulphate, and lime has to be added to precipitate the oxide. ”

“ The sulphurous pyrites are found, some massive, and others crystallized and disseminated in the rock; their colour, of a very clear golden yellow, does not indicate that they contain copper. They are mixed with fibrous sulphuret of iron,* (* Haarkies.) and nodules of swinestone, or fetid carbonate of lime. The marly stratum crosses the torrent; and, as the water washes out metallic grains, the people imagine, on account of the brilliancy of the pyrites, that the torrent bears down gold. ”

“ The upper end is concave, while the lower end has the original smooth surface of the concretion. Pyrite is found at Point Barrow in spherical masses of various sizes up to several pounds in weight. These spheres are nearly always cracked in two and scraped on the plane 575 surface for very obvious reasons. This gives the shape seen in Fort Simpson and Long Barrows specimen. ”

“ The arsenopyrite will not materially change the color of the fluid, but the other two turn it rose-red, and all give off the smell of sulphur. It looks sometimes like marcasite, but that is yellower, and has the fibrous structure, not found in arsenopyrite.
It is found in veins or in metamorphic rocks, associated with argentite, galena, sphalerite, chalcopyrite and pyrite. It is distinctly a mineral formed by deposition from hot vapors or hot water rising from either lavas, or in the course of metamorphism. ”

“ Late De Lesseps Collection. Collection of Mrs. Henry Draper. The obsidian is the typical stone of Mexico. Pyrites
Crystals of iron pyrites (pyrite, native iron disulphide) are sometimes used as amulets by the North American Indians, and the belief in their magic power is attested by their presence in the outfit of miscellaneous objects which the medicine-men use in the course of their incantations. ”

“ 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 ”

“ Then new layers of bruised pyrites were arranged so as to form an immense heap, the exterior of which was covered with earth and grass, several air-holes being left, as if it was a stack of wood which was to be carbonized to make charcoal. ”

“ Pyrites is a sulphureo-metallic substance, which cannot be produced by means of water, a substance which the influences of the atmosphere decomposes or separates into its elements, and which even our imperfect art may be considered as able to produce, by means of fusion in our fires. Therefore, the finding of this creature of fire intimately connected with those consolidated strata of mineral coal, adds the greatest confirmation, were it necessary, to the doctrine of those mineral bodies having been consolidated by fusion. ”

“ Very solid and compact masses of rock, such as greenstone, which are not easily affected by other means, are sometimes corroded by the chemical change of the pyrites contained in them, by which it is converted into a hydrate of iron [414] . In certain other rocks, which are also readily broken down by mechanical agents, clay-slate for instance, the disintegration is much accelerated by the decomposition of the pyrites. The oxydulous iron of [473] felspar is commonly converted by decomposition into a hydrate or ochre. ”

“ 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. ”

“ I was lately consulted with respect to the treatment of a pyritic ore in a very promising mine, but could not recommend the above treatment, because though the pyrites in the gangue was similar, the bulk of the lode consisted of silica, consequently there would be a great waste of power in triturating the whole of the stuff to what, with regard to much of it, would be an unnecessary degree of fineness. ”

“ 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. ”

“ The metallic sulphurets are, however, in many cases, separated from other tailings by washing immediately after the first amalgamation of the ore, and various devices have been employed for the treatment of such concentrated pyrites, which is often the richest in gold of all the constituents of the vein stuff. Following the analogy of natural decomposition, it has been repeatedly attempted, by roasting the pyrites in reverberatory furnaces, to drive off the sulphur and oxidize the metallic bases, so as to obtain a product containing fine particles of free gold. ”

“ They further observed that the heat is invariably found to be greatest in the blue and bluish-grey earth; that these earths almost always contain sulphuric acid; that they contain also sulphur, iron, alum, and gypsum; and lastly, that finely-divided particles of brass-coloured pyrites are visible throughout the whole of the beds when heat exists.
“Sulphuric acid is found in the hot beds above and below that which is the hottest, but this latter manifests no acidity that is sensible to the taste.
“Sulphuretted hydrogen is continually evolved from the clays containing the brass-coloured pyrites. ”