ORCIN. A crystallizable coloring mat ter obtained from the lechers, Varitgark Oreina.
ORES. (Germ. erne.) The mineral bodies from which metals are extracted. Metals exist in the ores in one or the other of the four following states : 1. In a metallic state, and either solitary or combined with each other ; in the latter case forming alloys. 2. Combined with sulphur, forming sulphurets. 8. Com bined with oxygen, forming oxides. 4. Combined with acids, forming carbonates, phosphates, &e., which generally go by the name of metallic salts.
Ores are very numerous. There are of Antimony 14 Ores.
Arsenic 10 Bismuth 5 Cobalt 12 Copper And so for others.
Certain ores which contain the metals most indispensable to human necessities have been treasured up by the Creator in very bountiful deposits, constituting either great masses in rocks of different kinds, or distributed in lodes, veins, nests, concretions, or beds with stony and earthy admixtures ; the whole of which become the objects of mineral explora tion: These precious stores occur in dif ferent stages of the geological formations ; but their main portion, after having ex isted abundantly in the several orders of the primary strata, suddenly cease to be found towards the middle of the secon dary. Iron ores are the only ones which continue among the more modern depo sits, even so high as the beds immedi ately beneath the chalk, when they also disappear, or exist merely as coloring mat ters of the tertiary earthy beds.
The strata of gneiss and mica-slate con stitute in Europe the grand metallic do main. There is hardly any kind of ore which does not occur there in sufficient abundance to become the object of mining operations, and many are found nowhere else. The transition rocks, and the lower part of the secondary ones, are not so rich, neither do they contain the same variety of ores. But this order of things, which is presented by Great Britain, Germany, France, Sweden, and Norway, is far from forming a general law ; since in. equinoctial America the gneiss is but little metalliferous ; while the superior strata, such as the clay-sehists, the sieni tie porphyries, the 'limestones, which complete the transition series, as also se vend secondary deposits, include the greater portion of the immense mineral wealth of that region of the globe.
All the substances of which the ordi nary metals form the basis, are not equal ly abundant in nature ; a great proportion of the numerous mineral species which figure in our classifications are mere va rieties scattered up and down in the cavi ties of the great masses or lodes. The workable ores are few in number, being mostly sulphurets, some oxides, and ear . bonates. These occasionally form of themselves very large masses, hut more frequently they are blended with Imps ' of quartz, felspar, and carbonate of lime, which form the main body of the deposit; as happens always in proper lodes. The , ores in that case are arranged in layers parallel to the strata of the formation, or in veins which traverse the rock in all directions, or in nests or concretions sta tioned irregularly, or finally disseminated in hardly visible particles. These depo sits sometimes contain apparently only one species of ore, sometimes several, which must be mined together, as they seem to be of contemporaneous forma tion; whilst, in other cases, they are se parable, having been probably formed at different epochs. Under the particular metals will be found an account of the lo calities of ores, &c. ; but the following general observations may prove useful in presenting a condensed resume of the whole subject.
1. Tin exists principally in primitive rocks, appearing either in interlaced mass es in beds, or as a constituent part of the rock itself; and more rarely in distinct veins. Tin ore is found, indeed, sometimes in alluvial land, filling up low situations between lofty mountains.
2. Gold occurs either in beds or in veins, frequently inprimitive rocks ; though it is also found in other forma tions, and particularly in alluvial earth. When this metal exists in the bosom of primitive rocks, it is particularly 1n schists ; it is not found in serpentine, but it is met with in greywacke in Transylva nia. The gold of alluvial districts, called gold of washing or transport, occurs, as well as alluvial tin, among the debris of the more ancient rocks.