MINERALOGY

Mineralogy – is the systematic study that deals with the characteristics of the individual and group of
minerals.

Minerals – are the building blocks of rocks, our planet. They form the earth and the bedrock that we live
on. The source of the basic inorganic commodities upon which our society relies. The sources of all
metals.

James D. Dana – developed the first widely used mineral classification system.

Solid – this gives the substance a definite shape and volume. Substance is not considered a mineral if it is
a liquid, gas, or plasma.

Made of atoms – every mineral is composed of atoms.

Crystalline Structure – a key characteristic of minerals is that their atoms are arranged in an orderly,
repeating pattern that extends in all three dimensions. This crystalline structure is responsible for many
of the physical properties that help mineralogists identify minerals, such as cleavage, hardness, and
optical properties.

Naturally Occurring - distinguishes minerals from synthetic substances, even if those synthetics mimic
the chemical and structural properties of naturally occurring minerals.

Inorganic - they are not the product of biological processes.

 Diamond - a naturally occurring, crystalline mineral made of pure carbon. It's the hardest known
natural mineral and is highly valued for its beauty and rarity.
 Fluorine (Fluorspar) – crystalline mineral made of calcium fluoride. Essential in manufacturing
optical lenses and as a source of fluoride for toothpaste and water treatment.
 Calcite – mineral that is made of calcium carbonate. Used in various industrial applications,
including construction materials like cement and concrete
 Mica – made of silicate compounds containing aluminum, potassium, and magnesium. Mainly
used in electrical insulators, cosmetics, and construction materials.

Symmetry – refers to a balanced and proportionate arrangement of parts that remains unchanged after
specific transformations, such as rotations or reflections.

Types of Symmetry

1. Mirror/Reflection Symmetry – symmetry with respect to a plane

2. Rotation Symmetry – symmetry with respect to a line
3. Inversion Symmetry – with respect to a point
4. Rotoinversion Symmetry – symmetry that combines rotation and inversion, handedness reverses
in these operations

The Seven Crsytal Systems - an approach for classification depending upon their lattice and atomic
structure.

Crystal System – refers to one of the many classes of crystals, space groups, and lattices. Method of
classifying crystalline substances.

Isometric (Cubic) System - has a unit cell in the shape of a cube. It is one of the most common and
simplest shapes found in crystals. All crystals of the isometric system possess four 3-fold axes of
symmetry, each of which proceeds diagonally from corner to corner through the center.

Two Variants:

 Body-centered cubic - has the lattice points in the middle of the unit cell
 Face-centered cubic - has the lattice points in the middle of each side of the cell.
Isometric crystal forms:

 Cube
 Octahedron
 Dodecahedron

Mineral with Isometric Crystal System

 Nickel - It is a silvery-white, lustrous metal that is highly resistant to corrosion and oxidation.
Nickel is widely used in stainless steel, batteries, coins, and as a catalyst in chemical reactions.

Tetragonal Crystal System - requires a set of 3 axes with two of the axes equal in length and the third axis
either longer or shorter than the other two.3 axes are naturally perpendicular to each other.

Mineral with Tetragonal Crystal System

 Wulfenite - is a lead molybdate mineral typically found in thin, tabular crystals with bright
orange, yellow, or red colors.

Orthorhombic Crystal System - we can place the crystal on three mutually perpendicular axes which are
of unequal length. This property is the defining characteristic of this group. In short, it is a three-axis
System each of which are mutually at 90° angles.

Mineral with Orthorhombic Crystal System

 Barite - a barium sulfate mineral known for its high density and commonly forms in tabular or
prismatic crystals.

Hexagonal System - is usually thought of as a 4-axis system. Three of the axes; commonly labeled a1, a2,
and a3; are equal in length and lie in a single horizontal plane that is perpendicular to the principal z axis.

Mineral with Hexagonal Crystal System

 Nepheline - a feldspathoid mineral commonly found in igneous rocks, usually appearing as gray,
white, or colorless crystals

Trigonal Crystal System - is defined by a 3-fold rotational or rotoinversion symmetry axis which
distinguishes it from other systems.

Mineral with Trigonal Crystal System

 Calcite - one of the most abundant minerals on Earth.

Monoclinic Crystal System - is defined by three unequal axes. Two of these axes are inclined at an
oblique angle to each other typically depicted vertically, while the third is perpendicular to the plane
formed by the other two usually shown horizontally.

Mineral with Monoclinic Crystal System

 Gypsum - A hydrated calcium sulfate mineral which is a common sedimentary mineral

Triclinic Crystal System - the least symmetrical of the seven systems, with no rotational axes or mirror
planes. Its three crystallographic axes are all inclined and of different lengths, forming no 90-degree
angles.

Mineral with Triclinic Crystal System

 Turquoise - A hydrous phosphate mineral renowned for its vibrant blue-green hues.

Crystallography – is the study of crystals and their structures, involving the analysis of the arrangement
of atoms within crystalline solids.

Crystallography is essential to civil engineering because many construction materials, like cement, are
polycrystalline.
Polycrystalline materials - are solids that consist of many small crystals (the “grains”).

Physical Properties of Minerals

 Hardness - one of the better properties of minerals to use for identifying a mineral. Hardness is
defined by how well a substance will resist scratching by another substance.
 The Mohs Scale - was created in the first half of the 19th century by the ĺ He selected ten
standard minerals, and arranged them in order of increasing hardness.
 Cleavage - A mineral's tendency to fracture along smooth, flat surfaces as a result of atomic
structural flaws is known as cleavage.
 Crystal Habit - The exterior look and form of a mineral's natural crystal development are referred
to as its "crystal habit."
 Density - is a measure of how tightly packed the atoms or molecules are within the mineral's
crystal structure.
 Streak - The streak of a mineral is the color of the powder left behind when the mineral is
rubbed against a hard, unglazed surface, like a streak plate.
 Fracture - is the way a mineral breaks when it does not exhibit cleavage.

Types of Fracture

1. Conchoidal - Smooth, curved surfaces, like broken glass (e.g., quartz).

2. Fibrous/Splintery Fracture - Breaks into thin fibers or splinters (e.g., asbestos).
3. Hackly Fracture - Jagged, rough surfaces, common in metals (e.g., native copper).
4. Uneven Fracture - Rough, irregular breakage (e.g., limonite).

Formation and Properties of Minerals

Main Mineral Formation Processes

1. Crystallization from Magma or Lava (Igneous Process) – As molten rock cools and solidifies,
minerals are created through a process called crystallization from magma or lava
Bowen’s Reaction Series:
 Discontinuous Series consists of minerals that undergo structural and compositional changes as
the temperature decreases.
 The Continuous Series, on the other hand, involves plagioclase feldspar, which gradually
transitions from being calcium-rich at high temperatures to sodium-rich at lower temperatures.
2. Precipitation – This happens when conditions like temperature, pressure, or chemical
composition change, reducing the solution’s ability to hold dissolved minerals.
3. Changes Due to Heat and Pressure (Metamorphic Process) – Metamorphism is the process by
which rocks change due to heat, pressure, or chemical activity, but without melting. During this
process, the minerals in a rock can either grow larger and become more organized, known as
recrystallization, or they can completely transform into new minerals through chemical
reactions.
4. Hydrothermal Processes (Mineral Deposition from Hot Fluids) – occurs when superheated,
mineral-rich fluids, often originating from magma, circulate through cracks and fractures in rocks
deep underground. As these fluids move, they dissolve various elements and minerals from
surrounding rocks.
Some notable hydrothermal deposits, including:
 Vein Deposits – formed by the deposition of minerals from fluids that fill open fractures or
cavities in rocks.
 Skarn Deposits – formed when hydrothermal fluids react with carbonate rocks, causing the
development of a metamorphic rock called a skarn.
 Epithermal gold deposits – formed at shallow depths (less than 1 km) and are typically
associated with recent volcanic activity.
Other Ways for Mineral Formation

Weathering - a natural process that gradually breaks down rocks and leads to the formation of new
minerals. It occurs due to exposure to environmental factors such as water, air, temperature changes,
and biological activity.

 Mechanical Weathering – happens when rocks break apart due to physical forces without any
change in their chemical composition.
 Chemical Weathering – transforms the minerals in rocks through reactions with water, oxygen,
carbon dioxide, and other chemicals in the environment, making them more stable under
surface conditions.

Key Processes:

1. Hydrolysis (Reaction with Water) - It occurs when water reacts with minerals, breaking down
their chemical bonds and forming new, stable minerals.
2. Oxidation (Reaction with Oxygen) - occurs when minerals containing iron react with oxygen
and water, forming iron oxides.
3. Carbonation (Reaction with Carbonic Acid) - occurs when carbon dioxide (CO₂) dissolves in
water to form carbonic acid (H₂CO₃), which reacts with carbonate minerals like calcite.
4. Hydration (Absorption of Water) - occurs when minerals absorb water molecules, causing
them to expand and change their structure.

Mineral Formation Through Organic Processes

Organic Formation – occurs when living organisms contribute to the creation of minerals. This process,
known as biomineralization, happens when organisms extract elements from their environment to build
hard structures like shells, bones, and corals.

How Organic Mineral Formation Occurs

1. Organisms Absorb Minerals from Their Environment

2. Biomineralization: Formation of Hard Structures
3. Accumulation and Sedimentary Rock Formation
4. Organic Decay and Mineral Precipitation