Mineral composition, textures and patterns of ores.

The mineral composition of metallical and nonmetallic natural minerals includes ore and nonmetallic minerals.

To a category ore usually refer magnesias and sulphides of heavy metals, native metals and intermetallic compounds; to a category nonmetallic - silicates, carbonates, halogens, sulphates, phosphates, borates and the native devices which are not possessing metallical properties. From minerals are extracted both the basic builders, and passing, concluded in them chemical and mechanical impurities. The minerals which are a part of ores, but not having commercial value, term accompanying. The quantitative relations of minerals in ores value on three categories: the main things (> 10 %), minor (1 - 10 %) and rare (<1 %).

The major devices of an interior constitution of ore bodies - their textural and structural features.

The ore texture is spotted by dimensional interposition of the mineral aggregates differing from each other on a composition, the shape, to the sizes and pattern.

Pattern of ore is spotted by the shape, the size and a method of a combination of separate mineral grains or their fragments in dimensionally isolated mineral aggregates.

Textures and patterns of ores of fields endogenic, it is endogenic - an exogenetic and exogenetic serial differ on morphological features and formation requirements. For each serial the characteristic groups and the subgroups of textures arising in ores of certain type in connection with displays of various geologic processes (tab. 1, tab. 2) are oozed.

Tab. 1. Genetic classification of textures of endogenic ores.

Tab. 2. Genetic classification of textures it is endogenic - exogenetic and exogenetic ores

Textures of endogenic ores

Textures of plutonic formation.

Textures of liquating and crystallisation differentiating of ore-bearing melting.

The interspersed texture characterises allocation of individual mineral isolations - crystals and their joints - in the form of inserts in containing intrusive formation.

Depending on quantity of an impregnation and its orientation ooze densely - it is absent-minded - oriented - interspersed textures.

Depending on quantity of blobs distinguish largely - (> 3mm), average - (1 - 3mm), small - (0,2 - 1mm), it is thin - (0,05 - 0,2mm) and it is dispersed interspersed (<0.05mm) textures.

The nodular texture characterises allocation of ore isolations of the roundish, oval or deplanate shape in the form of inserts in formations of the core and the ultrabasic composition. The sizes of nodules fluctuate over a wide range and sometimes reach in a diameter of 15 mm. Varieties of nodular textures - oriented - nodular, it is nodular - banded, densely nodular, transferring in massive, etc.

The nested texture characterises allocation of large, modular isolations of ore matter in containing intrusive formations. The sizes in a diameter reach to several see

The schlieren texture results from an inspissation of ore isolations in certain leases of intrusive formations. Isolations represent closely abutted either absent-minded phenocrysts or the small seats sometimes tracked by wedging light-duty streaks.

The pseudo-schistose texture is formed by alternation of bands in the intrusive formation, enriched or impoverished by ore matter.

Look-alike bands are oriented parallelly each other and often have sustained on power and extent character. Originating of pseudo-schistose textures speaks a crystallisation and gravitational differentia of ore-bearing melting.

The massive texture characterises a constitution of the ore almost totally consisting of different minerals quantity of accompanying minerals does not exceed 10 % of total amount. Ores with a massive texture develop one, two or the whole group of ore minerals. Their allocation can be uniform, non-uniform. In this connection distinguish varieties of massive textures - was uniform - massive, massive with devices banded, massive with devices bird's-eye, etc.

Textures of squeezing of ore melting on tectonic disturbances.

The venous texture results from performance by ore-bearing melting of large individual flaws in intrusive formations.

The vein texture is formed as a result of infiltration of ore-bearing melting into the light-duty flaws which are breaking down country rocks.

The mesh texture characterises a standing of ore matter in system of the flaws which are breaking down country rocks.

Brecciated - the cement texture is formed as a result of tectonic crushing of containing intrusive formations with the subsequent grouting of angular fragments by matter of ore-bearing melting.

Brecciated - the cement texture arises in that case. When to tectonic crushing fragile enough formations are plunged. Simultaneously originating grouting of fragments by ore matter result ins to their roundoff and roll-forming.

The line texture is formed as a result of viscous ductile travel of crystallising ore melting. Separate mineral aggregates in this case are elongated, lensed or are approximated.

Textures of postplutonic formation.

Textures of deposition of mineral matter from hydrothermal solutions in open vacuities.

The venous texture results from performance by ore or often venous matter of large flaws in containing rocks of a various composition.

The vein texture is formed as a result of deposition of ore and venous matter in the light-duty flaws which are breaking down country rocks. Varieties of vein textures: oriented - vein, parallelly - vein, a texture of cross of streaks, etc.

Cross texture it is vein widespread in ores of hydrothermal genesis. Its genesisis speaks numerous renewal of the tectonic movements tracked by deposition of hydrothermal mineralising. Cross of the streaks having a various mineral composition, quite often testifies to phasic character of ore-forming process.

The mesh texture grows out of deposition of ore and venous matter in system of flaws.

Brecciated - the cement texture is formed by a combination of fragments of mineral matter of the angular shape to cement of diverse composition and a constitution.

Brecciated - the cement texture differs from Brecciated - cement only rounded, approximated character of fragments of mineral matter.

Cockade texture variety Brecciated - cement or Brecciated cement. Round fragments of the manifold sizes and shapes cementing agent is laied out in a view rands a various configuration and power.

The banded texture characterises a constitution of the ore formed by a combination of consistently sidetracked aggregates of a various mineral composition or pattern.

The Crustyform texture a variety banded also characterises well appreciable legitimacy in formation of mineral aggregates of a various composition or a constitution, beginning from both walls of flaws to its central closure.

The drusy texture is caused by increase of brushes of crystals on walls of the hollows remaining free from mineral matter in process of infill it of gaping flaws.

The colloform texture is observed in the ores formed as a result of coagulation of colloidal solutions. Ore isolations have as a rule, a spheric constitution. Textures characterising a constitution of colloform aggregates have gained various namings: reniform, scalloped, globular, it is colloform - banded, etc.

The massive texture results from infill of an open vacuity by the mineral matter having an ore or venous composition.

The nested texture characterises a standing of separate ore isolations isometric or ungeometrical and the considerable sizes which are in a view of inserts in venous mass, executing an open vacuity.

The interspersed texture characterises a standing of individual mineral isolations of the small sizes in the venous mass executing an open vacuity.

Textures of metasomatic replacement.

For textures of this subgroup following features are characteristic:

1. Boundaries of neogenic and replaced aggregates have ragged, twisting character;
2. In mass of neogenic aggregates relicts - leases of country rocks are observed. Not undergone to replacement;
3. The morphological shape of textures often is inherited from primary textures of a replaced substratum.

Streak the visible texture is formed in difference from vein by selective metasomatic replacement by mineral matter about fracture room. A variety - a chain a visible texture.

The limbate texture results from selective replacement by ore or venous matter of peripheral bands of separate aggregates, their fragments or grains.

Inherited - the massive texture results from the full replacement of formation or ore the neogenic aggregate.

Inherited - the banded texture is formed as a result of process of selective replacement.

The interspersed texture of replacement is widely developed in ores of skarn type in areolas hydrothermal variation of country rocks.

The relict texture is caused by presence individual, ungeometrical, often small heels of a replaced substratum among mineral new growths.

Textures of metamorphic formation.

Textures of metamorphic transforming.

The banded texture arises in the course of ductile strain of nonuniform on a composition, often initially schistose ores.

The crenulated texture arises as effect of ductile strain of the ores rumpled in small crimps of various amplitude, intensity and orientation

The schistose texture characterises a constitution metamorphicly the conversed ore which one mineral individuals have got the oriented standing concordant with blanket orientation of mineral aggregates.

The texture spread outward results from a deplanation, a flexing and a crush of the separate fragile mineral aggregates which are in mass more ductile. A variety - an ocellar texture.

The texture brecciation arises in the ores which have undergone to intensive fragile strain. It characterises a constitution of the ore consisting of fragments of the various sizes, shapes, and a composition.

The boudinage texture arises in the ores, having the schistose constitution and undergone to intensive dislocation metamorphism is is not uniform.

Notching the texture characterises a constitution schistose or is nonuniform - banded ore, divided the short, promptly wedging flaws, oriented a cross or under an angle to a banding direction.

Textures of a metamorphic new growth.

The vein texture characterises a standing in room of the mineral matter mobilised by metamorphic solutions and sidetracked in thin flaws of ore or rock.

The venous texture characterises a constitution of the mineral matter formed also with involvement of the metamorphic sizes, but sidetracked in the open, gaping flaws of the considerable sizes.

The massive texture characterises a constitution of the ores having the uniform, close set, often monomineral adding up. Arise at the deep metamorphic processing of matter with variation of primary minute of a composition.

The banded texture characterises a constitution of the ores arisen in the course of the deep metamorphic transformings and possessing the nonuniform, banded constitution.

The interspersed texture characterises a constitution of the ores formed with involvement of metamorphic solutions. Such ores have sporadic, absent-minded character of allocation of ore matter.

Nested texture - a variety of the interspersed texture of ores in which one mineral aggregates reach the considerable sizes.

Textures it is endogenic - exogenetic ores.

Textures of postvolcanic formation.

Textures of metasomatic replacement. Textures of metasomatic replacement of ores of postvolcanic genesis on morphological features a little than differ from textures of ores of postplutonic genesis. Widespread following views: interspersed and nested replacements, veinlet, in separate leases - inherited - banded and inherited - massive. Distinctive feature of ores of this type - confinedness to metasomatic inflected volcanogenic or volcanogenic - to sedimentary strata.

Textures it is hydrothermal - sedimentary deposition.

Textures of the given subgroup characterise a constitution of the postvolcanic ores arising from hydrothermal solutions and return brines, volcanic exhalations and the emaniums arriving from ground depths. Deposition of ore masses originates at the bottom of reservoirs, is frequent in aggregate with naturally sedimentary chemogenic and terrigenous material. Ore aggregates take a form of deplanate lenticles, stratums, seats, phenocrysts, manifold concretions on quantity.

The schistose texture characterises a constitution of the ore formed by a combination of alternating deplanate mineral aggregates, differing from each other a composition, a constitution, power, in the extent, orientation. Varieties of textures: roughly schistose, it is thin schistose, non-uniformly - schistose, it is rhythmical - schistose, it is not clear - schistose, lentiform - schistose, etc.

It is layer by layer - the interspersed texture characterises a constitution of the schistose ore non-uniformly enriched small on quantity by ore inserts. Interiorly the constitution of the enriched stratums can be densely interspersed, is absent-minded - interspersed etc.

The concretion texture characterises a constitution of the precipitates consisting of magnesias of silica, aluminium, carbonates. Clustered aggregatess spheric, sometimes the pancake-shaped shape, having concentricallies - zonal are formed, the uniform interior constitution is more rare. The sizes fluctuate over a wide range. Depending on the sizes ooze following varieties: poppy 0,3 - 0,5mm, pea 2 - 5mm, bean 0,5 - 1sm, nut 1 - 3sm, monetary 1,5 - 2sm, pancake-shaped 2 - 15sm.

The detrital texture characterises an ore constitution in which one formation volcanic detonatings - explosions shared. Fragments represent mechanical chips of the ore matter fragmented as a result of explosive activity of a volcano. The shape of fragments - wrong, angular, sometimes roundish. The sizes different.

Massive texture widespread in ores volcanogenic - a sedimentary genesisis. Result from consecutive deposition a little differing on a composition, essentially ore stratums almost deprived of accompanying venous minerals.

The colloform texture is characteristic for ores is hydrothermal - a sedimentary genesisis. It testifies that deposition of mineral matter originated in the form of gel from colloidal solutions.

Textures of condensation of mineral matter from a gas phase.

As a result of an exit of hot volcanic gas in rather cold at the superficial bands of a volcano there is a crystallisation of mineral matter in the form of crusts. druses, powdery, nested and vein aggregations in flaws, round fragments and it is simple on a surface of igneous rocks. Process of deposition of solid matter of a gas phase by crystallisation is termed as condensation. Solid matter transition in a gas phase, passing liquid state, is termed as sublimating. Such aggregations usually have no industrial value.

Textures of exogenetic ores.

Aeolation textures.

Textures of chemical and mechanical variation

Textures of chemical and mechanical variation: fissured, porous, cavernous, wireframe, detrital, powdery, relict.

The fissured texture results from physical variation of primary ores and rocks by their mechanical fissuring. Occurrence of the small flaws collated in the whole system of jointing, promotes not only physical, but also to chemical transforming of mother substance.

The porous texture characterises dissolution of formations and the ores which have undergone to action of groundwater. Dissolution and core recovery of mineral matter originates usually selectively. In this connection there are the separate isolated small hollows, termed pores.

The cavernous texture is a variety of a porous texture. It characterises the ore or formation constitution penetrated by vacuities. Resulted leaching action of the superficial waters.

The wireframe texture has gained the name thanks to original, similar to a skeleton, to a constitution siliceous - the hydroxide aggregates remaining on a place of leaching before close set sulphidic ores.

The detrital texture characterises a constitution of the ores which have undergone the considerable physical and chemical variations. A detrital constitution those mineral aggregates which one have appeared inconvertible against chemical decomposition often have. Being accumulated in certain bands of a crust of aeolation, they form free-flowing aggregates.

The powdery texture characterises a constitution is rather thin crushed not the consolidated mineral matter consisting of fragments of the various shape and a composition. A variety of a powdery texture is earthy, crumbling.

The relict texture is among microtextures. It characterises a combination of the various mineral aggregates, one of which one is maintained in mass of another in the form of the small heels from replacement.

Textures of metasomatic replacement.

In the course of aeolation of rocks and ores along with physical and chemical fracture of primary mineral matter there is a formation of new mineral aggregates, inconvertible in the superficial requirements. Such mineral matter is deposited as by performance of pores, caverns, flaws and by metasomatic replacement of primary rocks or ores. To number of plutonic varieties of textures formed metasomatic by. The following is referred: veinlet, limbate, mesh, massive, interspersed, colloform.

The veinlets texture arises when again formed matter is laied out along the thin flaws having unrestrained, intermittent character.

The limbate texture results from selective replacement of primary minerals by matter - a new growth.

The mesh texture characterises a constitution of primary ores and the rocks densely penetrated by streaks of sec minerals.

The massive texture results from the full variation of a primary composition of ores. They are formed as a result of metasomatic transforming of primary aggregates.

The interspersed texture characterises a constitution and a standing in room of the sec mineral aggregates diffused in the form of separate inserts in mass of primary rocks or ores.

The colloform texture characterises a constitution and shapes of allocation of the mineral aggregates formed metasomatic by and at the same time possessing a metasomatic colloform constitution.

Texture of infill of vacuities.

The following is referred to number of the most widespread textures of the present subgroup: vein, mesh, it is brecciform - cement, crustal, drusy, colloform or incrusted.

The vein texture arises at grouting of open individual flaws in a primary ore substratum mineral matter of a sec genesisis.

The mesh texture arises in the presence of a dense network of flaws in the replaced primary mineral matter, spacefilled by minerals - new growths.

It is brecciform - the cement texture arises as effect of grouting of partially replaced fragments of primary ores or formations mineral matter of the superficial genesisis.

The crustal texture characterises a standing in room and the shape of allocation of the mineral aggregates sidetracked on a surface of fragments of primary ores or rocks, and also a standing and the shape of the mineral aggregates covering walls of large hollows of leaching - caverns.

The drusy texture characterises a constitution and character of a layout of the mineral aggregates consisting of well formed, closely accrete crystalline individuals, termed as druses or brushes.

The colloform or incrusted texture arises in the superficial requirements as a result of deposition of mineral masses by coagulation of colloidal solutions. Varieties: reniform, stalactite, stalagmitic, scalloped, globular etc.

Textures of sedimentary formation.

The originality of textures of the given group is caused by morphological features of the mineral aggregates formed chemogenic, terrigenous or biogene by at the bottom of reservoirs, representing oceans, the seas, lakes, the rivers, bogs. Such aggregates have usually deplanate, less often the approximated or wrong shape, and also fossils of the live organisms, occupying there are reservoirs where the sedimentogenesis took place.

The schistose texture is among the most abundant. It characterises the ore constitution, formed by a combination of consistently sidetracked deplanate mineral aggregates differing from each other by a composition or a constitution, and sometimes both a composition, and a constitution, often power and orientation of stratums. Such mineral aggregates have the sustained character on a direction of strata and change features of a constitution on the considerable spacing interval a little. It is possible to refer to number of varieties of schistose textures roughly schistose, it is thin schistose, non-uniformly schistose, rhythmically schistose, not clearly schistose, slantwise schistose, corrugated schistose etc. Look-alike views of textures are characteristic for sedimentary ores of iron, manganese, aluminium, for mineral salts, clays, sand, chalk-stones, dolomites etc.

Lentiform - the schistose texture characterises a constitution of the ore piled by promptly wedging, deplanate mineral aggregates sharply changing power.

The oolitic texture is a variety of a colloform texture. Separate oolite represents roundish concentricallies - zonal, small formation on the size. In which one central part often there is a small spall of quartz, a magnetite or other mineral. The look-alike spall serves as centre round which one there is a layer by layer deposition of dispersoid. The mineral composition of separate bands of oolite can be not identical. The ores formed by a major aggregation of oolites closely flanking to each other, are coherent often glass - clay or clay - carbonate matter.

The concretion texture arises in ores in those cases. When mineral matter stands apart in the form of enough large tens centimetres reaching in a diameter, spherical concretions.

The detrital texture characterises a constitution of separate stratums in sedimentary ores or the whole horizons piled coherent, is frequent differently the great, variously oriented fragments of a various composition, the shape and a constitution.

The organigenic texture characterises the ore constitution, containing the fossilized heels of organisms, more often blisters, or their fragments.

Structures of ores.

Detailed studying of structures of ores to be yielded usually in the course of studying polished schliff, that is caused small - and a fine-grained structure of the majority of ore formations. macroscopicly separate crystals can be installed only in rather coarse-grained units. In this connection at the macroscopical description of structures of ores it is possible to be restricted only to the performance of type of granularity, having subdivided structures on phaneric (it is large - average - and fine-grained) and ores with not clearly expressed or absolutely not expressed granularity. The last are characterised, thus, by cryptocrystalline or aphanic structure.

Except granular or crystalline structures at ores can be present and detrital structures. They are characteristic for ores of alluvial deposits and partly for ores of a sedimentary origin.

Except definition of structures on the size of mineral individuals, there is a division of structures on a method of a combination of separate grains, degrees of their idiomorphism, to type of mineral individuals.

For ores of a magmatic origin structures of decay of a firm mud are rather characteristic. The temperature of crystallisation of a firm mud from ore-bearing melting should be above temperature of decay of a solids. Temperatures of decay of a firm mud have gained the name of geological thermometers.

Sideritic structure a version of hypidiomorphic structure. In ores of this type Idiomorph rock-forming minerals - pyroxene, plagioclases etc., and intergrain gaps of these minerals settle down ore minerals. It is characteristic for ores of postmagmatic genesis.

For ores of postmagmatic genesis decay structures are characteristic also, are often observed poikilitic structures - sprouts of the most thin inserts of one ore mineral in other.

Deposits of mineral substance in open vacuities by the free crystallisation from muds form crystalline or granular structures, and by metasomatic replacement - metagranular structures.

For ores of a metamorphic origin are characteristic so-called blastic structures. Mineral individuals in such ores are often purified of additions as a result of a past recrystallization in a firm state

In endogenetic ores the structures which origin is related to fragile or plastic strain of mineral substance are often observed. Them term in the first case cataclastic, in second - buckling structures.

Structures of ores of an exogenetic origin: cryptocrystalline or cryptocrystalline. The sizes of individuals are so small, that the crystalline structure of ore can be installed only with use Roentgen-structure of the analysis. The mineral substance with aphanic structure at all has no crystalline structure.

Procedure of operation with a stone material.

Beginning operation with a stone material (samples of ores from deposits of various types), it is necessary to adhere to the following plan. Having viewed attentively the sample, it is necessary to read a label located in a box, and bindingly to understand completely a mineral composition of ore, using necessary manuals. Sometimes the small and absent-minded inferences of a mineral can appear main industrially valuable components of studied ore. For example, inserts Loparite (the size 1 - 2mm) in alkaline rock can to be noted simply, and this mineral spots value and integrated approach of ores from which it is taken niobium, tantalum, the titan and the rare earths.

After definition of a mineral composition it is necessary to pay attention to character of an arrangement of minerals in ore, to ooze and term mineral units present at it: phenocrysts, nests, nodules, spalls, cement, proveins, a great bulk, strips, borders, oolites, lenses, cakes etc.

Ratio of mineral units in ore it is spotted by concept "texture": interspersed, nested or spotty, nodular, brecciated, brecciated - cement, vein, aggregated, banded, limbate, oolitic, beaded, schistose, crustal etc. Having spotted a morphological view of a texture and knowing a mineral composition of ore, it is necessary to spot morphogenetic texture type, having taken advantage of genetic classification of textures endogenetic, it is endogenic - exogenetic and exogenetic ores. For example, it is brecciated - the cement texture can be met both in ores magmatic, and in ores of a postmagmatic origin. However having spotted, that ore contains spalls of rock of the basic composition, and cement is combined by sulphides, it is possible to say confidently, that the observable type of accretions to concern group of textures of squeezing of melting on tectonic infringements.

Having spotted morphogenetic texture type, it is possible then to characterise structural features of mineral substance in each separately taken mineral unit. For example, a rock structure, presented to ore spalls, fine-grained, and structure of ore sulphidic cement - average - or even coarse-grained. Having read and having viewed drawings in the grant, it is possible to gain representation and about other prominent features of the sulphidic unit, for example about presence at it of structures of decay of a firm mud etc. Studying of a mineral composition and a structure of ores is useful for accompanying sketches Stufe of samples.

Except ascertaining of mineral ratio in ores it is possible to spend and the analysis of sequence of formation of mineral units that allows to recreate vicissitude, and sometimes and a stage of ore-forming process, to rebuild conditions of accumulation of mineral substance.

Analyzing in further ratio of minerals and mineral units in ores of one type, it is possible to make the blanket plan of sequence of formation of minerals and a stage of their formation.