ENGINEERING & TECHNOLOGY

BY

BHORANIYA AHEMADABBAS A. (130460106008)

MINERALOGY : Mineralogy is that branch of geology which deals with various aspects related to minerals like mode of formation, composition, occurance, association, properties, uses, etc. In nature more than 2000 minerals are known to occur. The minerals may be divided in to two broad groups: (i) Rock forming minerals (ii) Ore forming minerals Rock forming minerals are those which are found in abundance in the rocks of the earth’s crust. Ore forming minerals are those which are of economic value and which do not occur in abundance in rocks.

Sr. No.

MineralGroup

Exampels

1 Oxides Quartz, Magnetite, Hematite Limonite etc.

2 Silicates Felspar, Mica, Horublende, Augite, Olivines, etc.

3 Carbonates

Calcite, Dolomite, Siderite, etc.

4 Sulphides Pyrites, Galena, Sphalerite, etc.

5 Sulphates Gypsum, etc.

6 Chlorites Rocksalt, etc.

Table No. 1

-> Common rock forming minerals : Rock forming minerals are very abundant in the earth’s crust. More than 1600 minerals species are known at present. Bust most of these are very rare and hence of academic interest only. According to an estimate 99.9% of the earth’s crust is composed of 20 – 25 rock forming minerals only. Economic minerals are therefore very scarce.

Table no. 2 shows the approximate chemical composition of the earth’s crust. Table no. 3 shows the minerals composition of rocks.

Sr. No.

Element Percentage

1 Oxygen 46.71

2 Silicon 27.69

3 Aluminium 8.07

4 Iron 5.05

5 Calcium 3.65

6 Sodium 2.75

7 Potassium 2.58

8 Magnesium 2.08

9 Titanium 0.62

10 Hydrogen 0.14

11 Phosphorus 0.13

12 Carbon 0.0094

13 Rest 0.5206

100%

SR. No.

Mineral

1 Felspar 59.5

2 Pyroxenes & amphiboles 16.8

3 Quartz 12.0

4 Biotite 3.8

5 Titanium 1.5

6 Apatite 0.6

7 Accessory mineral 5.8

→ FELDSPARSFeldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate

minerals that make up as much as 60% of the Earth's crust.Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar (see in fig.) is

→ PYROXENESThe pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems. Pyroxenes have the general formula XY(Si,Al)2O6 (where X represents calcium, sodium, iron+2 and magnesium and more rarely zinc, manganese and lithium and Y represents ions of smaller size, such as chromium, aluminium, iron+3, magnesium, manganese, scandium, titanium, vanadium and even iron+2). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes.

→ AMPHIBOLEAmphibole is the name of an important group of generally dark-colored, inosilicate minerals, forming prism or needle like crystals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown

Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. In chemical composition and general characteristics they are similar to the pyroxenes. The chief differences from pyroxenes are that (i) amphiboles contain essential hydroxyl (OH) or halogen (F, Cl) and (ii) the basic structure is a double chain of tetrahedra (as opposed to the single chain structure of pyroxene). Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes (at around 120 degrees), whereas pyroxenes have cleavage angles of approximately 90 degrees. Amphiboles are also specifically less dense than the corresponding pyroxenes. In optical characteristics, many amphiboles are distinguished by their stronger pleochroism and by the smaller angle of extinction (Z angle c) on the plane of symmetry. Amphiboles are the primary constituent of amphibolites

DIFFERENCE BETWEEN PYROXENES AND AMPHIBOLES

Quartzite (from German Quarzit) is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide (Fe2O3). Other colors, such as yellow, green, blue and orange, are due to other mineral impurities

Because of its hardness and angular shape, crushed quartzite is often used as railway ballast.Quartzite is a decorative stone and may be used to cover walls, as roofing tiles, as flooring, and stairsteps. Its use for countertops in kitchens is expanding rapidly. It is harder and more resistant to stains than granite. Crushed quartzite is sometimes used in road construction. High purity quartzite is used to produce ferrosilicon, industrial silica sand, silicon and silicon carbide. During the Stone Age quartzite was used, in addition to flint, quartz, and other lithic raw materials, for making stone tools.

→USES

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg,Fe)3AlSi3O10(F,OH)2. More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite. Biotite was named by J.F.L. Hausmann in 1847 in honour of the French physicist Jean-Baptiste Biot, who, in 1816, researched the optical properties of mica, discovering many unique properties.Biotite is a sheet silicate. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite) – both form in some rocks, in some instances side-by-side

→ TITANIUM : A metallic element, titanium is recognized for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment), lustrous, and metallic-white in color. The relatively high melting point (more than 1,650 °C or 3,000 °F) makes it useful as a refractory metal. It is paramagnetic and has fairly low electrical and thermal conductivity

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, named for high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6(F)2 and Ca10(PO4)6(Cl)2. Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material

∙ CIVIL ENGINEERING IMPORTANCE OF ROCK – FORMING MINERALS : Undoubtedly, among different minerals, economic minerals by virtue of their utility and inherent value, are very important and evoke interest. However, from civil engineering point of view, they are not relevant and, on the contrary, knowledge of rock forming minerals is very much necessary because:

(1) The civil engineering need to know the properties of rocks precisely to enable them to consider different rocks for various purposes such as foundation rocks, road metals, concrete aggregates, building stones, flooring material, roofing material, etc. All properties of rocks are in turn, dependent on the properties of their constituent minerals. Thus properties of civil engineering importance such as strength, durability, hardness, appearance, etc. Of rocks can be assessed only with the knowledge of the minerals that forms rocks.

(2) The economic minerals, since they are scrace, do not influence the properties of rocks and are hence irrelevant from the civil engineering point of view. But, if they happen to occur in large quantities, their economic value will not permit them to be used either as construction materials or as foundation sites.