Page 131 - SST Class 08

sedimentary rocks. Minerals brought out in their ferrous metals are generally more valuable than
raw or natural state from the earth’s depths are
called mineral ores. Ores have some impurities
and have to be processed before use.
Identification of minerals is done on the basis of
their physical and chemical properties. Colour,
hardness, ductility, conductivity, opacity and
solubility are the physical properties of minerals.
Colour
Minerals are of specific colours. Coal is black or
brown, while quartz may be black, red, purple or
pink.
Hardness
A mineral may be as soft as talc or as hard as a
diamond.
Ductility
A mineral may or may not be ductile; that is, it
may or may not be made into a thin wire by
beating or heating.
Opacity
Some minerals are transparent, such as glass, and
others are opaque such as iron.
Solubility
Minerals such as common salt, gypsum and
potash salts are soluble in water while quartz is
insoluble.
Classification of Minerals
Minerals are classified into metallic and non-
metallic categories.
Metallic Minerals
Metallic minerals are strong, ductile, and good
conductors of heat and electricity. They are mostly
found in the earth as ores. Iron, copper, silver and
gold are good examples of metals. Metallic
minerals can be further subdivided into ferrous
(containing iron) and non-ferrous (containing
metals other than iron).
Some common ferrous minerals are iron ore,
manganese ore, pyrite, chromite, nickel and
cobalt. Some non-ferrous metals are gold, silver,
copper, bauxite, lead, tin and magnesium. Non-
non-metallic ores.
Some metals are light while some are heavy.
Alloys are made by mixing two or more metals;
for example, bronze is an alloy of copper and tin.
Non-metallic Minerals
Non-metallic minerals include limestone, potash,
mica, nitrate and gypsum. They have wide
applications in different fields.
MINING
Generally minerals are located deep inside the
earth, but some of them can be found at or near
the earth’s surface. Extraction of minerals for
commercial purposes is called mining. The
ground from where minerals are excavated is
called a mine. A place should have enough or
abundant concentration of minerals to be mined.
The value of the metal or mineral is important for
mining. High value minerals like gold, diamond
and silver can be mined at a high cost, as they are
in great demand and are sold at high prices.
Different types of mines are used depending on
the location of minerals. Quarries are those mines
which are used to extract minerals located on the
surface. Minerals that lie at shallow depths are
taken out by removing the surface layers. This is
known as open-cast mining. Deep bores, called
shafts, have to be made to reach mineral deposits
that lie at great depths. This is called deep shaft
mining.
An open cast mine A quarry
Most of the minerals are bulky, such as iron and
coal. Transport facilities and cheap labour are
necessary for mining and transporting them to the
place of manufacture. The cost of mining minerals
Minerals and Energy Resources
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