Ore of cobalt is obtained in no other locality in India, and although zinc blende has been found elsewhere it is known to have been extracted only in this province.
It is, however, nearly always found associated with zinc blende, and with calamine, although only in small quantities.
Copper pyrites (copper), galena (lead), blende (zinc), cinnabar (mercury), &c. Of the sulphates we notice gypsum and anhydrite (calcium), barytes (barium) and kieserite (magnesium).
Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc blende, barytes, calcite and fluor-spar are common.
Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc, blende, barytes, calcite and fluor-spar are common.
Galena occurs in veins in the Cambrian clay-slate, accompanied by copper and iron pyrites, zinc-blende, quartz, calcspar, iron-spar, &c.; also in beds or nests within sandstones and rudimentary limestones, and in a great many other geological formations.
Zinc blende, however, being zinc sulphide, is not directly reducible by charcoal; but it is easy to convert it into oxide by roasting: the sulphur goes off as sulphur dioxide whilst the zinc remains in the (infusible) form of oxide, ZnO.
The difficulty in separating zinc blende from iron pyrites is well known, and probably the most elaborate ore-dressing works ever built have been designed with this end in view.
The ore, even if it is not blende, must be roasted or calcined in order to remove all volatile components as completely as possible, because these, if allowed to remain, would carry away a large proportion of the zinc vapour during the distillation.
If the zinc is present as blende, this operation offers considerable difficulties, because in the roasting process the zinc sulphide passes in the first instance into sulphate, which demands a high temperature for its conversion into oxide.
For the desulphurization of zinc blende where it is not intended to collect and save the sulphur there are many mechanical kilns, generally classified as straight-line, horse-shoe, turret and shaft kilns; all of these may be made to do good work on moderately clean ores which do not melt at the temperature of desulphurization.
In roasting a ton of rich blende containing 60 per cent.
Zinc sulphide, ZnS, occurs in nature as blende (q.v.), and is artificially obtained as a white precipitate by passing sulphuretted hydrogen into a neutral solution of a zinc salt.
An impure form of the salt is prepared by roasting blende at a low temperature.
Magnetic pyrites, copper pyrites, zinc blende and arsenical pyrites are other and less important examples, the last constituting the gold ore formerly worked in Silesia.
It is often associated with blende and pyrites, and with calcite, fluorspar, quartz, barytes, chalybite and pearlspar as gangue minerals; in the upper oxidized parts of the deposits, cerussite and anglesite occur as alteration products.
BLENDE, or Sphalerite, a naturally occurring zinc sulphide, ZnS, and an important ore of zinc. The name blende was used by G.
The term "blende" was at one time used in a generic sense, and as such enters into the construction of several old names of German origin; the species under consideration is therefore sometimes distinguished as zincblende.
Crystals of blende belong to that subclass of the cubic system in which there are six planes of symmetry parallel to the faces of the rhombic dodecahedron and none parallel to the cubic faces; in other words, the crystals are cubic with inclined hemihedrism, and have no centre of symmetry.
An important character of blende is the perfect dodecahedral cleavage, there being six directions of cleavage parallel to the faces of the rhombic dodecahedron, and angles between which are 600.
When chemically pure, which is rarely the case, blende is colourless and transparent; usually, however, the mineral is yellow, brown or black, and often opaque, the depth of colour and degree of transparency depending on the amount of iron present.
Crystals of blende are of very common occurrence, but owing to twinning and distortion and curvature of the faces, they are often rather complex and difficult to decipher.
A compact variety of a pale liver-brown colour and forming concentric layers with a reniform surface is known in Germany as Schalen- blende or Leberblende.
A few varieties of blende are distinguished by special names, these varieties depending on differences in colour and chemical composition.
A pure white blende from Franklin in New Jersey is known as cleiophane; snow-white crystals are also found at Nordmark in Vermland, Sweden.
Black blende containing ferrous sulphide, in amounts up to 15 or 20% isomorphously replacing zinc sulphide, is known as marmatite (from Marmato near Guayabal in Colombia, South America) and christophite (from St Christophe mine at Breitenbrunn near Eibenstock in Saxony).
Transparent blende of a red or reddish-brown colour, such as that found near Holywell in Flintshire, is known as "ruby-blende" or "ruby-zinc."
Pfibramite is the name given to a cadmiferous blende from Pfibram in Bohemia.
Blende occurs in metalliferous veins, often in association with galena, also with chalcopyrite, barytes, fluorspar, &c. In oredeposits containing both lead and zinc, such as those filling cavities in the limestones of the north of England and of Missouri, the galena is usually found in the upper part of the deposit, the blende not being reached until the deeper parts are worked.
Blende, is also found sporadically in sedimentary rocks; for example, in nodules of clay-ironstone in the Coal Measures, in the cement-doggers of the Lias, and in the casts of fossil shells.
Beautiful isolated tetrahedra of transparent yellow blende are found in the snow-white crystalline dolomite of the Binnenthal in the Valais, Switzerland.
It was discovered in 1875 through its spectrum, in a specimen of zinc blende by Lecoq de Boisbaudran (Comptes rendus, 1875, 81, p. 493, and following years).
The metal is obtained from zinc blende (which only contains it in very small quantity) by dissolving the mineral in an acid, and precipitating the gallium by metallic zinc. The precipitate is dissolved in hydrochloric acid and foreign metals are removed by sulphuretted hydrogen; the residual liquid being then fractionally precipitated by sodium carbonate, which throws out the gallium before the zinc. This precipitate is converted into gallium sulphate and finally into a pure specimen of the oxide, from which the metal is obtained by the electrolysis of an alkaline solution.
It occurs in the uncombined condition and alloyed with iron in meteorites; as sulphide in millerite and nickel blende, as arsenide in niccolite and cloanthite, and frequently in combination with arsenic and antimony in the form of complex sulphides.
Twinning according to the first law is effected by rotation about an axis normal to the sphenoidal face (III), the resulting form resembling the twins of blende and spinel.
It occurs in metalliferous veins, often in association with iron-pyrites, chalybite, blende, &c., and in Cornwall and Devon, where it is abundant, with cassiterite.
In the vicinity there are the most important deposits of zinc and lead in the state, and the city derives its name from the deposits of sulphide of lead (galena), which were the first worked about here; below the galena is a zone of zinc carbonate (or smithsonite) ores, which was the main zone worked between 1860 and 1890; still lower is a zone of blende, or zinc sulphide, now the principal source of the mineral wealth of the region.
Zinc-blende occurs in large masses at Ammeberg, near the northern end of Lake Vetter.
The Francke-Tina process, named from Francke, German consul at Bolivia, and tina, the wooden vat in which the process is carried out, was developed in Bolivia for the treatment of refractory ores rich in zinc blende and tetrahedrite (fahl-ore).
Another metallic sulphide, blende, ZnS, is of importance for Germany, Belgium and the United States, much less so for the United Kingdom, as a source of sulphur.
Blende contains only about half as much sulphur as good pyrites, and this cannot be burned off as easily as from pyrites, but this" roasting "has to be done somehow in any case in order to prepare the ore for the extraction of the zinc.
The roasting of blende is nothing like so easy as that of pyrites, since the heat developed by the oxidation of the zinc sulphide itself is not sufficient for carrying on the process, and external heat must be applied.
This operation is both more costly and more delicate than the roasting of pyrites, but it is now perfectly well understood, and gas is obtained from blende furnaces hardly inferior in quality to that yielded by pyrites kilns.
To begin with, in the burners pyrites (or, as the case may be, brimstone or blende) is made to yield hot burner-gas containing about 7% (in the case of brimstone 10 or 11%) of SO 2.
The principal ores are galena, sphalerite or zinc blende and smithsonite or zinc carbonate, which is locally called "dry bone" and which was the first zinc ore mined in the state.