SEV217 Engineering Geology and Surveying Assessment item 1— Assignment 1 Due date: Friday Week 12 (1 June 2012) Weighting: 20% Length: As required ASSESSMENT Objectives This assessment item relates to...

Microsoft Word - solution
Question 1-1
(a) A mineral is a naturally occu
ing, solid, inorganic substance [may be
compound/element] having a fixed/variable (within certain limits) chemical
composition and has a definite atomic structure.
Different types of mineral crystal forms exist as per isometric/non-isometric axes.
Some crystal forms are sketched below:-
Different types of rock forming minerals are as below:-
(i) Minerals such as Hematite, Magnetite have magnetic properties.
(ii) Minerals such as Quartz, Feldspar etc. have non-magnetic properties.
(iii) Minerals such as Tourmaline are Pyro electric minerals i.e. they produce
electricity when heated.
(iv) Minerals such as Quartz are piezoelectric minerals i.e. they produce electricity
when pressurized.
Above mentioned and other minerals form rocks as given below. They give
identification to the rock. Below are some igneous rocks.
(i) Granite consists mainly of Quartz, Orthoclase feldspar with biotite & garnet as
accessory minerals.
(ii) Pink Granite consists of Quartz, Orthoclase feldspar with hornblende as
accessory mineral.
(iii) Charnockite consists of Orthopyroxene, Quartz and Feldspar.
(iv) Basalt consists of Plagioclase feldspar and clinopyroxene.
(v) Peridotite consists of Olivine as the dominant mineral and clinopyroxene as
other mineral.
Below are some sedimentary rocks.
(i) Shale consists of clay minerals (e.g. illite, kaolinite).
(ii) Sandstone consists of Quartz and feldspar.
Below are some metamorphic rocks.
(i) Mica schist consists of muscovite, biotite and sillimanite.
(ii) Ma
le consists of Calcite mineral.
(iii) Amphibolite consists of Hornblende, plagioclase feldspar.
Now, the above mentioned rocks are having quite varying engineering usages.
E.g. Granite is used for heavy engineering works for
idge piers, columns, retaining
walls, etc. Quartzite which is a metamorphic rock is also used in the same way as
Granite but is not used for ornamental works as it is
ittle. Ma
le is used for
flooring and stone facing slabs. Whereas Limestone is used as an aggregate for
concrete and also as a base material for cement. Thus, we see that the rocks must be
identified so as to decide its suitability for engineering work. Now, two rocks having
same minerals can have quite varying engineering properties as the properties depend
not only on minerals but also on their a
angement in the crystal structure of the rock.
So to identify such rocks the only way is to first identify it’s constitute minerals by
their properties such as color, cleavage, streak, hardness etc. and the final
identification by checking the rock sample in a microscope if necessary.
(b) Formation of rocks:-
The three types of rocks get formed as below:
Igneous rocks are formed by crystallization of molten rock material i.e. is melt formed
at depth. From there they move up due to buoyance force as they are lighter then
Magma. If they get formed in this way below the surface of the earth, where the
molten rock is called magma, they cool very slowly and thus have large grain size.
If magma reaches surface of the earth, it is called lava. Lava cools faster and so thus
formed igneous rocks have fine grains. Now, the igneous rocks get weathered over a
large period of time and get converted into finer...