This is about engineering geology in which we study rocks and minerals.

1. Rocks and Minerals

2. 2.1Introduction: Minerology
The study of minerals is called mineralogy. A mineral is a is a naturally occurring
element or chemical compound that is normally crystalline and that has been
formed as a result of geological processes. The mineral has a characteristic
chemical composition, a highly ordered atomic structure, and specific physical
properties. Minerals range in composition from pure elements and simple salts to
very complex silicates with thousands of known forms.

3. 2.2. Minerals and rocks
A mineral is a naturally occurring solid with a definite chemical composition and a
specific crystalline structure. A rock is an aggregate of one or more minerals. (A
rock may also include organic remains and mineraloids.) Some rocks are
predominantly composed of just one mineral. For example, limestone is a
sedimentary rock composed almost entirely of the mineral calcite. Other rocks
contain many minerals, and the specific minerals in a rock can vary widely. The
vast majority of the rocks of the Earth's crust consist of quartz, feldspar, mica,
chlorite, kaolin, calcite, epidote, olivine, augite, hornblende, magnetite, hematite,
limonite and a few other minerals.

4. 2.3.Industrial Minerals and Ores
Some minerals, like quartz, mica or feldspar are common, while others have been
found in only four or five locations worldwide. Over half of the mineral species
known are so rare that they have only been found in a handful of samples, and
many are known from only one or two small grains. Commercially valuable
minerals and rocks are referred to as industrial minerals. Rocks from which
minerals are mined for economic purposes are referred to as ores.

5. 2.4.Identification of common minerals
The most common minerals can be identified by inspecting or testing their
physical properties as follows.
2.4.1Color (use your eyes)
Primarily, the color of a mineral is noticed. However, color itself is not enough to
identify a mineral. Chemical impurities often change the color of a mineral without
changing its basic makeup.
2.4.2Streak (use porcelain plate)
When a mineral is rubbed firmly across an unglazed tile of white porcelain (a
streak plate), it leaves a line of powder. This is called the streak. The color of the
streak is always the same, whether or not the mineral has impurities. For example,
quartz leaves a white streak, whether it is violet (amethyst), pink (rose quartz), or
brown (smoky quartz).
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6. 2.4.Identification of common minerals
2.4.3Magnetic (use magnet)
If a mineral is magnetic, a magnet will stick to the mineral. Magnetism is caused
by the presence of iron and is useful is identifying iron oxides.
2.4.4Hardness (use your fingernail, the coin, and the nail)
Hardness is defined as resistance to abrasion or shape change when force is
applied. Hardness can be measured on the Mohs scale. It was created in 1812 by
the German mineralogist Friedrich Mohs. The Mohs hardness scale places ten
common or well-known minerals on a scale from one to ten. One is the softest
mineral and ten is the hardest. Table 2-1 presents the minerals used in the Mohs
hardness scale while Table 2-2 presents the common objects and their Hardness
values

7. Table 2 .1Mohs Harness Scale
1 2 3 4 5 6 7 8 9 10
Talc Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond
Table 2 1Mohs Harness Scale