This chapter is dedicated to the study of mineral matter, which are
the inert (non-living) materials that constitute the mountains, valleys,
deserts, etc. In nature there are two types of mineral matter: rocks
and minerals. The difference between them is that the minerals
are the elements that constitute the rocks, which means that rocks are
always made by two or more kinds of minerals. This is easily seen if
you look at a piece of granite, like the one shown in the photo below.
It can be noticed that it is not made by only on substance, but three.
There are white-greyish, white and black particles.
The white-greyish particles are the mineral called "quartz".
The white particles are the mineral called "feldspar"
" The black particles are the mineral called "mica
of the observed particle is called mineral particle and each type
of particle is called mineral species. The photo shows that there
are many mineral particles but only three types of mineral particles:
to do. Read
the explanation on the concept of minerals and the classification of them
and do the "Multiple Choice Test 5". Then read the text on the
properties of minerals and mineral deposits and do the exercises "Identification
of minerals and their properties 5" also "Crossword 5".
. Mineral. A mineral is a natural, inorganic,
solid, crystal matter with a fixed chemical composition
or a composition that vary between very narrow limits.
1.1 What does
natural mean? A substance is called natural when it is originated
in nature, that is to say, without human intervention. The matter
produced by humans is called artificial material. For example,
cement and steel are not minerals, since not found in nature but they
are products manufactured by humans.
1.2 What does
inorganic mean? A natural substance is called inorganic when it
does not constitute nor characterize organisms, in other words,
when it is not made of carbon (C) and hydrogen (H) atoms. Those are
the two essential elements that form the organic matter, which is the
one that composes the organisms. An example of an inorganic material
is sodium chloride (NaCl) and an examples of an organic matter are the
lipids composed mainly with C and H.
1.3 What does
a solid matter mean? A substance is called solid when the particles
(atoms, molecules or ions) are tightly bound and occupying fixed
positions. This means that a force must be used to deform or break
it. Thus, for a substance to be considered as a mineral, it is necessary
to be solid. The water is not a mineral, nor is the oxygen of the air,
etc. The usual saying "mineral water" does not mean that the
water is mineral but that it came from the inside of the mountain, that
is from a mine of water.
1.4 What does
crystal mean? A solid matter is called crystal when its particles
are arranged, that means the particles are not placed in any shape,
but in fixed locations, such that, if the sufficient space is available,
they form geometric shapes such as cubes, prisms, pyramids, etc.,
which are called crystals. When the number of particles is big
enough, the crystals are visible to the naked eye.
In exhibitions and
trades of minerals, we often speak of "crystallized minerals"
when crystals are visible to the naked eye, and "mineral mass"
when they are not. Actually, the second ones are also mad of crystal
matter. Only by observing them under a microscope we can appreciate
its small microscopic crystals. When hard minerals are formed, they
can be exploited to make a durable jewelry. Large crystals are very
rare and that makes them highly prized. When solid particles are unordered
they are said to be amorphous solid matter.
By the unit cell
we call the crystal as small as possible, that is constituted by
the minimum number of particles (atoms, molecules or ions). A crystal
visible to the naked eye is not more than a repetition, sometimes an
infinity and in the three dimensions of space, of the unit cell. .
1.5 What does
having a defined chemical composition mean? The minerals have a
chemically defined composition when the ratio of the chemical elements
forming it is constant or has only minor variations. For example
the galena ore has a sulfur atom per each
atom of lead. It can also contain atoms of silver, gold and other elements,
but without exceed 0.3% (called "impurities") if otherwise
it is no longer called galena but a different
1.6 The fake
minerals or mineral-look-alike. They are natural, inorganic and
solid substances as limonite, opal and obsidian,
that are not authentic minerals, because its particles are unordered,
that is they are the amorphous matter. Also considered as mineral-look-alikes
are inorganic liquids which can be found in nature, such as wate and
. The classification of minerals. Scientifically, the minerals
are classified according to their chemical composition, but this classification
precise to have a knowledge of chemistry that are dealt with in the courses
superior to this one. Therefore, the following is the classification of
minerals according to its usefulness. In this classification, two large
groups are differentiate:
2.1 The non-metallic
minerals. They are not used to obtain metals. The principal
(such as quartz, orthoclase
feldspar, albite feldspar, biotite
mica or black mica, muscovite mica
or white mica and olivine),
(such as calcite and aragonite),
(as gypsum), and
- salts (as
halite and sylvite).
Most of those minerals
are associated with other minerals to form rocks, and because of that
they get the name of petrogeneric minerals. The principal are
silicates, since they are the ones that make a majority in rocks
forming the mountains (forms rocks such as granite,
porphyry, basalt and clay). Then, there are carbonates,
because the calcite is the main mineral in the
limestone which also forms many mountains.
metallic minerals. They are used to obtain metals. Usually
they don't form rocks and can be found in small quantities, that is
why is needed to use mines in order to reach them. When extracting,
usually are attached to pieces of rocks. The metallic mineral that is
extracted is called ore and the rock that accompanies is called bargain.
Below is a table of the main minerals grouped by ore that is obtained
from them. The diamond is also included,
for being the most appreciated for their hardness beauty.
metallic minerals and diamond.
names of the photographs minerals are shown in blue)
minerals (Fe): Oligist,
y siderite. The iron is used in
the constructions of houses and in manufacturing machines.
(Cu): Chalcopyrite, azurite,
malachite, and native
Cooper is used as a conductor of electricity, manufacture of boilers,
pipes and coins; and exterior coating.
(Pb): Galena. Lead
is used to manufacture pipes, as a protection for the radiation
and to produce pigments for paints.
Zinc is used to protect roofs and exterior doors;
and to protect the iron (galvanized).
minerals (Al): Bauxite.
is used to make cars, doors, windows and kitchen utensils.
(Sn): Cassiterite. Tin
is used to protect iron (tin).
(Hg): Cinbabar. Mercury
is used for the manufacture of thermometers and barometers.
(S): Pyrite and native sulfur.
given its high percentage of sulfur, does not work to get iron,
only to produce sulfuric acid.
(Au): Native gold. Gold
is used in jewelry and for making coins.
(Ag): Argentite and native
is used in jewelry, coins and in photography.
minerals (Pt): Native platinum.
is used in jewelry and to promote chemical reactions in industry.
(C): Diamond. Given
its hardness is used to make drills and cutting and polishing tools.
Choice Test 5. (Spanish
activity. Activity in English is under construction)
. The properties of minerals. There are three types of properties:
geometric, physical and chemical properties.
Within these three, can be distinguish the following types:
Exfoliation and Tenacity
Radius, Brightness and Refraction
Effervescence with HCl
GEOMETRIC PROPERTIES. Are related to the shape of
crystals. The most important is symmetry.
Symmetry is defined as the existence of an object oriented equally but
in different directions. For example, a cube presents symmetry respect
to an imaginary axis of rotation, passing through the center of one
side and the center of the opposite face, since by rotating the cube
relative to said imaginary axis, one of its faces repeats four times.
MECHANICAL PROPERTIES. Are
the properties related to the application of force on the crystal. The
main ones are hardness, toughness and exfoliation.
The hardness of a mineral is the resistance to being scratched. The
more tightened the particles are, the harder it is. A mineral can be
both hard and fragile, because although the bonds are strong if the
structure has little stability, it can be broken easily. For example,
the diamond, which is the hardest mineral that exists, is quite fragile.
In 1920, German
mineralogist F. Mohs proposed a ladder of ten levels of hardness, in
which each mineral radius is scratch by the one that lays in higher
level. The Mohs ladder is:
- Can be scratched
by nail: 1 . Talc and 2 .
- Can be scratched
by razor: 3 . Calcite and 4 .
- Can be scratched
by file: 5 . Apatite and 6 .*Ortosa
- Can scratch
glass: 7 . Quarz, 8 .
Topaz, 9 . Corundum and
10 . Diamond
(hardness 2) is cut with calcite (hardness 3)
Is the ability of some matters to break, resulting in flats.
This is due to the existence of "binding forces between particles"
which is differenced depending on the considered direction. Some minerals,
when receiving hits, break into cubes, such as galena, other
into slices, such as gypsum and micas, others into octahedrons,
as fluorite, etc. The results, crystals, are called exfoliation
solids. In the market of collectors, they are not as valued as
natural forms. Specialists in cutting gemstones (gemologists), before
deciding to work a piece, examine it carefully to deduce the possible
cleavage planes. Non-exfoliation minerals when broken show uneven surfaces
dominated by fractures. For example conchoidal fracture
(in shape of shells) characteristic of quartz, splintery,
galena is exfoliated into cubes
Toughness. Is the resistance of a mineral to deform or break,
which is the separation of its particles. According to this feature
there are several types of minerals:
When force is used, they recover to the primary shape.
When force is used, they do not recover to the primary staying deformed.
When stretch, yarns may result.
When smashed, can get the shape of thin sheet.
When force is applied, they break easily without getting a shape of
mica crystals are elastic
OPTIC PROPERTIES. Are
related to the behavior of light influencing the mineral. The main ones
are color, stripe color, brightness and refraction.
Color. The color of a mineral is the kind of light
that reflects when illuminated. It is one of the most efficient
characteristics for identification. Some minerals may present different
colors, depending on the type and amount of impurities they contain,
resulting in the so-called "varieties". For example
the mineral quartz, can occur in the varieties:
pure quartz, also called hyaline
quartz or crystal rock (which
is colorless), smoky quartz (black), rose
quartz (pink), amethyst (purple),
citrine lemon yellow) etc.
Color of stripe or plain stripe. Is the color
of the mineral powder. It is called stripe color because usually
mineral dust is obtained by pressing the mineral against a plate porous
of white porcelain and drawing a line on it, as if using a chalk on
a blackboard. Depending on the color of the mineral stripe it can match
its surface or be completely different. For example, pyrite is golden
and the stripe is black. The color of the stripe is very useful for
pyrite is golden and the stripe is black
Brightness. The brightness of a mineral is a degree
to which the light is reflected from its surface. There are brillant
minerals and mate minerals. The most popular types of brightness
are: metallic, vitreous, silky, pearly,
adamantine, resinous and crass (greasy).
Refraction. Is the change of direction that is
experienced by a beam of light while passing from one medium to another.
The light, firstly passes from air to the mineral, and if it is transparent,
then back to the air. In some minerals the light beam during the pass,
split into two beams, leaving two images. This phenomenon is called
birefringent. The transparent variety of calcite called Island
spar, which is an example of birefringent mineral. The minerals
which do not exhibit this behavior are called monorefringent,
for example rock salt or halite
are monorefringent minerals.
spar is a mineral birefringent
ELECRIC PROPERTIES. Are those that relate to electrical current.
The best known is the conductivity, which is the ability to pass an electric
Are those associated with magnetism, which is the ability to attract
the iron. Some minerals like polar magnetite
are able to attract small iron such as nails, tacks, etc. and deflect
a compass needle. Others minerals present lower degree of magnetism, whereby
its magnetism is only detectable when pulverized and by the magnet approaching
to see whether it attract particles or not. .
attracts iron clips
CHEMICAL PROPERTIES. Are those properties that depend on the
ability of the mineral to react chemically with other substances.
The most important are the solubility and the effervescence with hydrochloric
The solubility in water. The soluble minerals can
have taste and odor. For example halite
is salty, slivina is salty and spicy, epsom
salt is bitter, etc.
The effervescence with hydrochloric acid (HCl).
The ability of a mineral to react with the acid by realizing bubbles
and carbon dioxide (*CO2). This reaction is useful to identify the calcite
ans aragonite, which are te basic minerals
produces effervescence upon contact with hydrochloric acid
. The mineral deposits. The
minerals deliver to humankind chemical elements that society needs for
the industry. For example iron, lead, fluorine, sulfur, etc. Usually to
get them having a mine is required, which is a vertical wells
from which goes horizontal galleries. These are elongated along
the seams or ore veins. In a mine the mineral matter
is called ore and accompanying rock, gangue. Nowadays, many
mineral deposits are being exploited opencast. This type of operation
is done by blasting with dynamite. Then with the aid of shovels,
minerals are loaded on a truck to the shredders.
The mineral reserves
are logically limited, because of that every time it is necessary to recover
the chemicals already use and prevent them from ending up in rivers and
the sea, where it is almost impossible to recover them for reuse. At present,
much of the iron melt in the furnace is obtained from scrap. This process
is known as one example of the recycling of metals.
On the other hand,
some chemicals such as mercury (thermometers and batteries), nickel and
chromium (nickel and chrome industries), are very poisonous and cause
mortality of fish and aquatic birds, so it also necessary to recycle instead
of throwing into the aquatic environment.
minerals and properties of minerals 5. (Spanish
activity. Activity in English is under construction)
activity. Activity in English is under construction)