Lesson 3: Rock – Forming Minerals 7.

SPECIFIC GRAVITY
 Specific gravity is the weight of the mineral compared to the weight of
All about Minerals an equal volume of water. Native metals are the heaviest ones.
8. OTHER PROPERTIES
Mineralogy is the science that deals with the study of minerals. It is an
 MAGNETISM, ODOR, TASTE, REACTION TO ACID,
important discipline for many reasons. The study of the earth’s crust gives
FLUORESCENCE
scientists an idea of how the earth was formed. The discovery of new minerals
o For example, magnetite is strongly magnetic
could provide useful materials for industries. Studying the chemical properties
o Sulfur has distinctive smell
of minerals could lead to discoveries of new uses for earth’s mineral
resources. Minerals have always been an important part of the society since o Halite is salty
the time of prehistoric man. Early humans carved tools out of quartz. Pottery o Fluorite has the ability to ultraviolet rays to visible light
has been made of various clays since ancient times. Table salt or halite has o Calcite fizzes with acid as with dolomite but in powdered form.
been used in food preservation for millions of years and is still in use today.
MINERAL GROUPS
Minerals defined
A more stable and less ambiguous basis for classification of minerals is by
In Chemistry, mineral is any naturally occurring chemical element or chemical composition.
compound, but in mineralogy and geology, minerals are chemical elements or
1. Silicates
compound that have been formed through inorganic processes.
 minerals containing 2 of the most abundant elements in the Earth’s crust,
Guide Question no. 01 - How can we say that something is a mineral? namely, silicon and oxygen.
 Over 90% of the rock-forming minerals belong to this group. Aside from
To say that something is a mineral, it must have all the following Silicon (46.6 %) and Oxygen (27.7%), the other most common elements
characteristics: that make the earth’s crust are Al (8.1), Fe (5.0), Ca (3.6), Mg (3.1), Na
(2.8) and K 2.6).
1. It is naturally occurring (not man-made or machine generated) 2. Oxides
2. It is inorganic (not a byproduct of living things)  minerals containing Oxygen anion (O2) combined with one or more
3. It has a definite arrangement of atoms, that is solid with an orderly metal ions
crystalline structure 3. Sulfates
4. Its chemical composition can be expressed in terms of chemical  minerals containing Sulfur and Oxygen anion (SO4) combined with
formula. other ions
4. Sulfides
 minerals containing sulfur anion (S2) combined with one or more ions.
Some sulfides are sources of economically important metals such as
copper, lead and zinc.
5. Carbonates
 minerals containing the carbonate anion (CO3) combined with other
elements
6. Native Elements
 minerals that form as individual elements.
PROPERTIES OF A MINERAL o Metals and Inter-metals – minerals with high thermal and electrical
conductivity, typically with metallic luster, low hardness (gold, lead)
More than 3000 minerals are known and most of them are characterized by o Semi-metals – minerals that are more fragile than metals and have lower
definite chemical composition, crystalline structure, and physical properties. conductivity (arsenic, bismuth)
o Nonmetals – nonconductive (sulfur, diamond)
1. LUSTER - the quality and intensity of reflected light exhibited by the
7. Halides
mineral.
 minerals containing halogen elements combined with one or more
 Metallic – generally opaque and exhibit a resplendent shine similar to a
elements
polished metal.
 Non-metallic – (glassy), silky, pearly, dull (earthy), greasy, among Minerals make up the rocks beneath your feet, the soil that supports plants,
others. and the deep rock of Earth’s mantle. Any thorough study of Earth must
2. HARDNESS - is the measure of the resistance of a mineral to abrasion. include an understanding of minerals. But it is not sufficient to study minerals
Mohs scale is used to determine the hardness of a mineral. isolated from the rest of the planet. Rather we can learn more by observing the
3. COLOR – the color of a fresh surface mineral is a clue to their ways that minerals interact with other Earth systems.
identification. A lot of minerals can exhibit same or similar colors.
Individual minerals can also display a variety of colors resulting from Minerals are naturally occurring, (not man-made or machine-generated)
impurities and also from some geologic processes like weathering. inorganic, (not a byproduct of living things) solid with an orderly crystalline
4. STREAK - is the mineral’s color in powdered form. structure and a definite chemical composition. Minerals are the basic building
 Examples of streak: pyrite exhibits gold color but has a black or dark blocks of rocks.
gray streak.
A. Physical Properties
 Color – The color of a mineral depends on the elements which
constitute the crystal lattice
– the arrangement of atoms, or groups of atoms, in a
specific pattern and with high symmetry. The reflection of certain
wavelengths of light by the crystal lattice results in the color
perceived by the observer.
5. CRYSTAL FORM
 Streak – refers to the color of the mineral in its powdered form
 The form reflects the supposedly internal structure of the mineral. It is
 Luster – refers to the relative differences in the opacity and
the natural shape of the mineral before the development of any cleavage
or fracture. transparency of a mineral as light is reflected on its surface. This
describes the “sparkles” of the mineral surfaces.
 Specific gravity – refers to the ratio of the weight of the mineral of
the water with an equal volume. This parameter indicates how
many times more the mineral weighs compared to an equal amount
of water.
 Hardness – refers to the measure of the resistance of a surface to
6. CLEAVAGE AND FRACTURE
abrasions or scratches. It is generally measured using the Mohs
 Cleavage is the property of some minerals to break along specific
Scale of Hardness.
planes of weakness to form smooth, flat surfaces
 Cleavage – refers to the tendency of the mineral to be split or
 These planes exist because the bonding of atoms making up the
broken along flat surfaces
mineral happens to be weak in those areas.
 Fracture – refers to the texture or shape of the mineral’s surface
 Some minerals do not break along cleavage planes but instead it is
when the mineral breaks into forms other than flat surfaces
described as fracture, which is irregular or without any definite pattern
or direction
  Tenacity – refers to the behavior of the mineral under deformation
or stress such as cutting, crushing, bending, or hitting.
 Crystal habit – refers to the growth crystal pattern of a mineral as
single or aggregated
B. Chemical Properties
 Solubility – refers to the ability of a substance to dissolve in a
solvent at a specified temperature.
 Melting point – refers to the temperature at which solid turns into
liquid. Minerals composed of atoms that are tightly bonded within
the crystal structure have high melting points.

Although there are thousands of mineral, only very few groups are involved in
rock-formation. Major rock-forming minerals are feldspar, quartz, micas,
pyroxene, olivine, calcite and dolomite.

All about Rocks

Why do we study rocks? All earth processes in some way depend on the
properties of these basic materials. Every rock contains clues about the
environments in which it is formed. For example, some rocks are composed of
entirely small shell fragments. This tell us that the particles composing the
rock originated in shallow marine environment. Other rocks contain clues
indicating that they originated from a volcanic eruption or deep in earth during
Minerals are natural substances that have a definite crystal structure. Minerals
mountain building. Thus, rocks contain vast information about events that
are the building blocks that make up rocks. There are three main types of
have occurred over the earth’s long history.
rocks. Igneous rocks are created when molten rock cools and solidifies.
WHAT ARE ROCKS? When particles of sand, silt, or other small particles are compacted and
cemented together, sedimentary rocks are formed. Metamorphic rocks are
Rocks are naturally formed, non-living mass of organic and inorganic earth created when one type of rock undergoes a transformation due to heat,
material consisting of one or more minerals that are held together in a firm, pressure, or chemical reactions. The process that breaks down rocks is
solid mass weathering. Erosion is the process by which rocks or rock particles are
moved from one place to another place. The process that illustrates the
THREE TYPES OF ROCKS - There are three types of rocks: igneous, changes between types of rocks is referred to as the Rock cycle.
sedimentary and metamorphic. Through changes in conditions one rock type
can become another rock type or it can become a different rock of the same Minerals in the Society
type.
Earth’s crust is the source of a wide variety of minerals, many of which are
1. IGNEOUS ROCKS – are rocks that form from the cooling of hot useful and essential to people. As a matter of fact, all manufactured product
molten masses called magma (hot molten mass that can be found contains materials obtained from minerals. Most people are familiar with the
beneath the earth’s surface) or lava (hot molten mass on the earth’s common uses of basic metals, including Aluminum in beverage can, Copper in
surface). electrical wires, Gold in jewelry, and Silicon in computer chips. But fewer are
aware that pencil Lead does not contain Lead metal but is really made of the
soft black mineral called graphite. Baby powder is made from mineral talc
with added perfume. Mineral quartz is used for ordinary glass, and drill bits
which is used by your dentist is impregnated with pieces of diamond, the
hardest mineral. These are only some of the minerals that we are using in our
2. SEDIMENTARY ROCKS – are formed by the compaction and
everyday lives. The economic uses of rocks and minerals are important to us.
cementing together of sediments (materials that settle out of air and
Consequently, a basic knowledge of the earth materials is essential to the
water), broken pieces of rock-like gravel, sand, silt, or clay.
understanding of all Earth science phenomena.

USES OF SOME MINERALS

3. METAMORPHIC ROCKS – are formed when igneous or