Transcript Mineral
Enrollment no. Name 130450106044 Shah ishani 130450106045 Shah richa 130450106046 Shrimali pritesh 130450106043 Rasikbhai munir A ‘mineral’ may be defined as a nautural ,inorganic,homogenous,solid substance having a definite chemical composition and regular atomic structure. The various physical properties of minerals are: 1) form (habit) 2) colour 3) streak 4) lustre 5) cleavaqge 6)fracture This is one of the first observation made when a minearl is examined in a hand specimen. The form represent the common mode of occurance of a mineral. It is also called habit and structure of minerals. 7) hardness 8)specific gravity 9) transparencty 10) tenacity 11) fluorescence 12) phosphorescence The colour of mineral is due to absorption of certain wave length of while light by atoms making up the crystal. The remaining wave lengths of white light that are not absorbed ,give rise to colour seen by observer. So dark coloured minerals absorb most of light whereas red minerals reflect or transmit mainly red light and absorb all others. The colour of the mineral powder is called streak. It is more consistent and reliable than the body of colour of the mineral. The streak is obtained by rubbing a mineral against an unglazed porcelain plate called the ‘streak plate’ Luster is the nature of shining on the surface of the mineral. It is a measure of the reflectively of light of the mineral surface. Based on the quality or type of shining ,lustures,are grouped as metallic or non metallic. It is defiend as the tendency of crystallized mineral to break along certain definite directions,yielding more or less smooth,plane surfaces. The plane along the mineral break are called cleavage planes. The fracture of mineral may be defined as the appearance of the randomly broken surface. In case of fracture,the breaking should be in any other direction than the cleavage. Cleavage appear as smooth and shining surfaces, but fracture do not produce smooth surfaces. Hardness is defined as the resistance of a mineral to abrasion,or scratching. It is one of the most important diagnostic properties of mineral. Hardness of mineral is studied either as absolute hardness or as relative hardness. Specific gravity is a number which represent the ratio of the weight of mineral to the weight of an equal volume of water. The weight of water should be taken at 4⁰ C Temprature. Transparency of a mineral may be defiend as its capability to pass light through a mineral , it may be called as transparent. This character of a mineral depends on chemical composition , imprities , inclusion, weathering and also thickness form muscovite is not transparent but the same mineral in thin layers is perfectly transparent. The behaviour of a mineral towards the forces that tend to break ,bend , cut or crush it is described by the term tenacity. Various type of tenacity are: 1) Sectile 2) Malleable 3) Brittle 4) flexible Some minerals when exposed in sunlight, produce a color quite different from their own. The property of minerals is called fluorescence. Some minerals glow and emit light when they are placed in ultraviolet light or certain other electrical radition . The glow induced in the minerals may continue for a few second or minutes after the removel of the cause. This property of minerals is called phosphorescence. Rocks may be defined as aggregate of minerals. Some rocks such as quartz and marble , contain grains of one mineral only but most are composed of a varity of different minerals. 1) igneous rocks 2)sedimentary rocks 3)metamorphic rocks Igneous rocks are formed by coolong and solidifiaction of magma. The term magma is applied when the melt is underground.the same,when it reaches the earths surface and flows over it,is called lava. The igneous rocks are characterized by Presence of crystalline minerals and interlocking texture. Formed from a high temprature rock melt The volcanic igneous rocks are always extermely fine grained Examples= granite,basalt,dolerite Sedimentary rocks are formed by consolidation and cementation of the sediments deposited under water. Sediments are the product of weathering. Since these are secondary materials ,the rocks formed out of them are called sedimentary rocks. Sedimentary rocks are characterized by Lamination and bedding or stratification. Cross bedding or current beding Occurance of fossils Occurance of tracks and trails Occurance of mud cracks ,rain prints example=sandstone , limestone,dolomite Metamorphic rocks are formed when the preexisting rocks have been changed in texture and composition by increased temperature and pressure. The metamiorphic rocks generally have following features Some minerals like kyanite, garnets which are the product of metamorphism are found only in metamorphic rocks. Usually, metanurphic rocks are composed of coarse grained minerals. Clssified in to two parts 1) primary structure 2) secondary structure Primary structure further sub divided into two types A) those which are caused by the mobility or viscosity of magma. B)those which are caused by surrounding environment and the manner in which magma cools. Sometimes igneous rocks shows parrallel or sub parallel bands or streaks which are caused by flow of magma during coling and crystallization are called flow structure. spherulitic structure is characterised by presence of thin mineral fibers of various sizes arranged in perfect radial manner about centre. Orbicular structure is characterised by presence of ball like segregations. In this structure volcanic igneous rock appears to be made up of numerous parallel polygonal prismatic columns bundled together. This is result of contraction of lava during cooling. In this structure rocks appear to be made up of number of sheets,because of development of nearly horizontal craks . This is effect of erosion over rocks formed at depth. The structure of sedimentary rocks can be classified into three groups. 1)mechanical structure 2)chemical structure 3)organic structure Mechanical structure include all those structure that have been devloped in sedimentary rocks due to some physical processes at the time of deposition of sediments. The important mechanical structure are bedding,lamination and cross lamination , ripple marks, rain marks , jaints and cracks. ripple marks are the symmetrical or unsymmetrical undulation that may be seen on some sedimentary deposits. These are caused by winds or waves,during deposition of sediments in shallow water environment In unconsolidated or partially consolidated sediment deposits,joints often devlop because of shrinkage due to water loss,compaction and settlement. These joints are characteristically short,irregular and discontineous . Chemical structure include those features that are produced during the segregation of surfaces of sediment deposits during chemical process. The importants structure are, 1) concretionary structure 2) o- olitic and pisolitic structures 3) geode structures The important structures are, 1) cataclastic structure 2) schistose structure 3) gneoissose structure 4) maculose structure 5) granulose structure It is produced under the infulence of direct pressure in upper zones of earths crust. Due to this shoft rocks like shales develop cleavage and hard rocks are shattered to produce crushed breccias. It the rock consits of broadly parallel or subparallel layers or bands of flaky ,platy or rod like minerals making it very weak in direction of parallelism,such a texture is called schistose structure. In this structure ,bands or folia of platy and flaky minerals alternate with those equidimensional and granular minerals These bends are generally of contrastring colours,composition and textures. It is characterised by spotted appearance of the rock that may be caused due to formation of large sized crystal within fine grained rocks. It is rock is composed predominantly of equidimensional minerals,then nither segreegation nor foliation takes place .such a texture is called granulose structure.