Cambrian, Ordovician and Silurian beds have been recognized, the Upper Cambrian consisting of a limestone which is very rich in metalliferous ores (especially galena and calamine).
Silver, gold, lead and copper ores occur in many localities.
Soriano xx.-F/ores 12.
The table below gives the average production of zinc, argentiferous lead, iron-pyrites and other ores during the quinquennial period 1901f 905.
Other ores - 36O 68,376
Iodide and chloro-bromide of silver, and argentiferous Silver lead ores, the largest deposits of the metal being found in the last-mentioned form.
In unlimited supply, important deposits of rich iron ores suitable for smelting purposes; and for the manufacture of steel of certain descriptions abundance of manganese, chrome and tungsten ores are available.
Magnetite, or magnetic iron, the richest of all iron ores, is found in abundance near Wallerawang in New South Wales.
At many of the mines at Kalgoorlie, Western Australia, large quantities of ores of telluride of gold have been found in the lode formations.
Zinc ores, in the several varieties of carbonates, silicates, oxide, sulphide and sulphate of zinc, have been found in several of the Australian states, but have attracted little attention except in New South Wales, where special efforts are being made successfully to produce a high-grade zinc concentrate from the sulphide ores.
The manganese ores of the Bathurst district of New South Wales often contain a small percentage of cobalt - sufficient, indeed, to warrant further attempts to work them.
Copper and lead are found in several parts of the Aravalli range and of the minor ridges in Alwar and Shaikhawati, and iron ores abound in several states.
These ores were worked by the ancients, but so inefficiently that their spoilheaps can be smelted again with profit.
From Cartagena the principal exports are metallic ores, esparto grass, wine, cereals and fruit.
The former are of great commercial importance, being, in most cases, valuable ores, e.g.
With regard to the imports into Russia-they consist mainly of raw materials and machinery for the manufactures, and of provisions, the principal items being raw cotton, 17% of the aggregate; machinery and metal goods, 13%; tea, 5%; mineral ores, 5%; gums and resins, 4%; wool and woollen yarns, 32%; textiles, 3%; fish, 3%; with leather and hides, chemicals, silks, wine and spirits, colours, fruits, coffee, tobacco and rice.
In 1859 the mines were worked only for their gold; the ignorant miners threw away the " black stuff " which was really valuable silver ore with an assay value four times as great as that of their ores of gold; and when this was discovered there came a period of unprecedented silver production.
The Tonopah ores were richer in silver than in gold, the respective values in 1904 and 1905 being approximately in the proportion of three to one.
Of Tonopah, rich ores were found in the Goldfield District, and within three years there were 8000 people in this region.
In the production of silver Nye county ranked first in 1907 ($3,667,973, of which $3,544,7 88 was from Tonopah), Churchill county second ($432,617, from Fairview, Wonder and Stillwater), and Eureka county (with lead silver ores) and Storey county were third and fourth respectively.
Considerable quantities of the following minerals have been found: barytes (heavy spar), magnetite (magnetic iron ore), and pyrolusite (manganese dioxide) in Humboldt county; roofing slate in Esmeralda county; cinnabar (ore containing quicksilver) in Washoe county; haematite in Elko and Churchill counties; cerussite and galena (lead ores) in Eureka county; and wolframite (a source of tungsten) at Round Mountain, White Pine county.
The problem of the profitable treatment of the sulphide ores has been practically solved here.
Iron ores are widely distributed within the state, and there have been times since the eve of the War of Independence when the mining of it was an industry of relatively great importance.
There are many rich deposits of iron ores in the state, but they only produce a small quantity of charcoal iron for local consumption.
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.
Barytes is of common occurrence in metalliferous veins, especially those which yield ores of lead and silver; some of the largest and most perfect crystals of colourless barytes were obtained from the lead mines near Dufton in Westmorland.
The ores found here comprise silver-free galena, sulphate of zinc and calamine.
The hornsilvers all occur under similar conditions and are often associated together; they are found in metalliferous veins with native silver and ores of silver, and are usually confined to the upper oxidized parts of the lodes.
They are important ores of silver (the pure chloride contains 75.3% of silver), and have been extensively mined at several places in Chile, also in Mexico, and at Broken Hill in New South Wales.
The Egyptians obtained silver, iron, copper, lead, zinc and tin, either pure or as alloys, by smelting the ores; mercury is mentioned by Theophrastus (c. 300 B.C.).
Stromeyer detected a new metallic element, cadmium, in certain zinc ores; it was rediscovered at subsequent dates by other observers and its chemical resemblance to zinc noticed.
Sefstrom definitely proved the existence of a metallic element vanadium, which had been previously detected (in 1801) in certain lead ores by A.
This has led to the estimation of sugar by means of the polarimeter, and of the calorific power of fuels, and the valuation of ores and metals, of coal-tar dyes, and almost all trade products.
He wrote Correlation Papers - Archaean and Algonkian (1892), Some Principles Controlling the Deposition of Ores (1901).
The iron ores mined at Daiquiri near Santiago are mainly rich hematites running above 60% of iron, with very little sulphur or phosphorus admixture.
Iron-ores are known;at several places on the outskirts of the alpine tracts (as about Irkutsk), as well as in the Selenginsk region and in the Altai.
The chief lead ores are galena and cerussite; of minor importance are anglesite, pyromorphite and mimetesite (qq.v.).
Lead ores are smelted in the reverberatory furnace, the ore-hearth, and the blast-furnace.
In the blast-furnace all lead ores are successfully smelted.
In smelting at once in the same blast-furnace ores of different character, the old use of separate processes of precipitation, roasting and reduction, and general reduction prevailing in the Harz Mountains, Freiberg and other places, to suit local conditions, has been abandoned.
Ores are smelted raw if the fall of matte (metallic sulphide) does not exceed 5%; otherwise they are subjected to a preliminary oxidizing roast to expel the sulphur, unless they run too high in silver, say 100 oz.
The leading reverberatory furnace for roasting lead-bearing sulphide ores has a level hearth 14-16 ft.
In making up a charge, the ores and fluxes, whose chemical compositions have been determined, are mixed so as to form out of the components, not to be reduced to the metallic or sulphide state, typical slags (silicates of ferrous and calcium oxides, incidentally of aluminium oxide, which have been found to do successful work).
The lead produced in the reverberatory furnace and the ore-hearth is of a higher grade than that produced in the blast-furnace, as the ores treated are purer and richer, and the reducing action is less powerful.
Iron ores have been found in most of the states, and are especially abundant in Minas Geraes.
Gold, lead, copper and iron ores occur as veins.
The gold is found in minute particles arid in the richest ores the metal is rarely in visible quantities before treatment.
Grains of metallic tin occur intermingled with the gold ores of Siberia, Guiana and Bolivia, and in a few other localities.
Throughout the world, primary deposits of tinstone are in or closely connected with granite or acid eruptive rocks of the same type, its mineral associates being tourmaline, fluorspar, topaz, wolfram and arsenical pyrites, and the invariable gangue being quartz: the only exception to this mode of occurrence is to be found in Bolivia, where the tin ore occurs intimately associated with silver ores, bismuth ores and various sulphides, whilst the gangue includes barytes and certain carbonates.