Lab 3A: An Introduction to Minerals
ESS 101 Lab 3A: An Introduction to Minerals | ESS
101: Introduction To Geology And Societal Impacts
Lab 3A: An Introduction to Minerals
Learning Goals
By completing this lab, students will learn:
● The technical definition of a mineral
● The different physical properties of a mineral and how they form
● How to use common diagnostic properties to identify a mineral
A. Minerals
Introduction
Minerals are the basic building blocks that make up the solid Earth. Therefore, any study
of the solid Earth must begin with an understanding of minerals.
A mineral, by definition, is a (1) naturally occurring, (2) solid, (3) usually inorganic
element or compound with a (4) definite crystalline structure and (5) chemical composition which
varies only within specific limits. Common examples are quartz, diamond, garnet, talc, and
halite (salt).
Some useful tips for what a mineral is/isn’t:
(1) Although compounds produced in a laboratory can have many of the
characteristics of a mineral, they are not naturally occurring and
therefore are not minerals.
(2) Minerals are solids, therefore liquids and gases are not considered
minerals.
(3) Nearly all minerals are inorganic, that is, not produced by living
organisms.
(4) Minerals have a distinct crystalline structure (Figure 3-1). Each mineral
has an orderly, predictable arrangement of atoms. For example, the
minerals graphite and diamond are both made of carbon, but what makes
them unique is a significant difference in the way the atoms are arranged
(Figure 3-1). (A mineraloid differs from a mineral in that it lacks crystalline
structure (i.e., is amorphous). For example, opal is a mineraloid; it has the
same composition as quartz but lacks the crystal structure.)
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, Lab 3A: An Introduction to Minerals
(5) Minerals have a definite chemical composition that can be expressed
as a specific chemical formula. Quartz, for instance, is composed of silicon
and oxygen and has the formula SiO2. Some minerals have more complex
compositions. Garnet's formula, for instance, is A3B2(SiO4)3, where A and
B represent a variety of elements such as Ca, Mg, Fe, and Mn. Although
2
, Lab 3A: An Introduction to Minerals
the exact composition of garnet can vary, the ratio between A and B is
constant — 3 atoms of A for every 2 atoms of B.
Figure 3-1 The atomic structure of (a) diamond and (b) graphite. Diagrammatic
inserts show bonding relationships of carbon atoms. In diamond, each carbon
atom is strongly bonded (covalent bonds) to four adjacent carbon atoms. In
graphite, each carbon atom is strongly bonded to only three neighboring atoms.
Strongly bonded atoms in graphite occur in sheets, which are only loosely
attached to one another by weak van der waal forces.
The above diagrams represent the atomic structures of two solids. The spheres represent
atoms that are bonded together.
1. Which of the above atomic structures is representative of a mineral (A or B)?
3
ESS 101 Lab 3A: An Introduction to Minerals | ESS
101: Introduction To Geology And Societal Impacts
Lab 3A: An Introduction to Minerals
Learning Goals
By completing this lab, students will learn:
● The technical definition of a mineral
● The different physical properties of a mineral and how they form
● How to use common diagnostic properties to identify a mineral
A. Minerals
Introduction
Minerals are the basic building blocks that make up the solid Earth. Therefore, any study
of the solid Earth must begin with an understanding of minerals.
A mineral, by definition, is a (1) naturally occurring, (2) solid, (3) usually inorganic
element or compound with a (4) definite crystalline structure and (5) chemical composition which
varies only within specific limits. Common examples are quartz, diamond, garnet, talc, and
halite (salt).
Some useful tips for what a mineral is/isn’t:
(1) Although compounds produced in a laboratory can have many of the
characteristics of a mineral, they are not naturally occurring and
therefore are not minerals.
(2) Minerals are solids, therefore liquids and gases are not considered
minerals.
(3) Nearly all minerals are inorganic, that is, not produced by living
organisms.
(4) Minerals have a distinct crystalline structure (Figure 3-1). Each mineral
has an orderly, predictable arrangement of atoms. For example, the
minerals graphite and diamond are both made of carbon, but what makes
them unique is a significant difference in the way the atoms are arranged
(Figure 3-1). (A mineraloid differs from a mineral in that it lacks crystalline
structure (i.e., is amorphous). For example, opal is a mineraloid; it has the
same composition as quartz but lacks the crystal structure.)
1
, Lab 3A: An Introduction to Minerals
(5) Minerals have a definite chemical composition that can be expressed
as a specific chemical formula. Quartz, for instance, is composed of silicon
and oxygen and has the formula SiO2. Some minerals have more complex
compositions. Garnet's formula, for instance, is A3B2(SiO4)3, where A and
B represent a variety of elements such as Ca, Mg, Fe, and Mn. Although
2
, Lab 3A: An Introduction to Minerals
the exact composition of garnet can vary, the ratio between A and B is
constant — 3 atoms of A for every 2 atoms of B.
Figure 3-1 The atomic structure of (a) diamond and (b) graphite. Diagrammatic
inserts show bonding relationships of carbon atoms. In diamond, each carbon
atom is strongly bonded (covalent bonds) to four adjacent carbon atoms. In
graphite, each carbon atom is strongly bonded to only three neighboring atoms.
Strongly bonded atoms in graphite occur in sheets, which are only loosely
attached to one another by weak van der waal forces.
The above diagrams represent the atomic structures of two solids. The spheres represent
atoms that are bonded together.
1. Which of the above atomic structures is representative of a mineral (A or B)?
3
