Understanding Earth LEC 172 Lecture 4 Reading
Ch 3; Earth Materials: Minerals & Rocks
What are Minerals?
Mineralogy =
1. The branch of geology that studies the composition, structure, appearance, stability, occurrence, and
associations of minerals
2. The relative proportions of a rock’s constituent minerals.
Mineral = A naturally occurring, solid crystalline substance, generally inorganic, with a specific chemical
composition.
Minerals are:
Homogenous – they can’t be divided mechanically into smaller components.
Naturally occurring – Must be found in nature (e.g., Diamonds mined in S Africa are minerals, but lab
produced ones are not minerals)
Solid (1) Crystalline Substances (2) – (1) Solid substances (not liquid or gas) & (2) have atoms arranged
in orderly repeating 3D arrays.
Usually inorganic substances – exclude materials composed of organic C in plant/animal bodies.
However, they can be secreted by organisms.
Have a Specific Chemical Comp. – Uniqueness is determined by the chemical comp., & arrangement
of atoms w/in the internal structure.
Amorphous/glassy materials – those that lack an orderly internal arrangement e.g., Windowpane glass.
The Structure of Matter:
Atoms the smallest unit of an element that retains the physical/chemical properties of the element.
The Structure of Atoms:
Nucleus – the centre of the atom, containing virtually all the mass and 2 types of particles:
a) Proton - +vely charged. Atoms of the same element have the same No. of Protons.
b) Neutrons – Electrically neutral. Atoms of the same element may have differing No. of Neutrons.
Electrons - -vely charged. Negligible mass (~0). Surround the nucleus in a moving cloud. No. of Electrons = No.
of Protons so overall atomic charge = 0.
Atomic Mass & Number:
Atomic Number = The number of protons w/in the nucleus. Defines the type of element. Also, the number of
electrons.
Elements in the same Group (vertical column) tend to have similar chemical properties.
Atomic Mass = Sum of the No. of Protons & Neutrons. Atoms of the same element may have differing Atomic
Masses, resulting from differing No.’s of Neutrons (but same Protons) …
Isotope = Atoms of the same element w/ different No.’s of neutrons.
Chemical Reactions:
, Chemical Reactions = interactions of the atoms of 2 or more chemical elements in certain fixed proportions
that produce chemical compounds.
The structure of an atom determines its chemical reactions with other atoms.
Chemical compounds, such as minerals, are formed by either:
Electron Sharing = the mechanism by which a covalent bond is formed between the elements in the
chemical reaction. Or
Electron Transfers = the mechanism by which an ionic bond is formed between the elements in the
chemical reaction.
Ion = An atom or group of atoms that has an electrical charge (+/-) because of the loss/gain of 1 or more
electrons.
Cation = A positively charged ion.
Anion = A negatively charged ion.
Chemical Bonds:
When chemical compounds are formed either via electron sharing/transfer, the ions/atoms that make up the
compound are held together by electrostatic attraction between -ve electrons & +ve protons.
The attractions or chemical bonds, between shared or lost/gained electrons can be strong or weak.
Strong bonds prevent a compound from decomposing into its elements or other compounds and keep
minerals hard and from cracking/splitting.
Ionic Bonds –
The simplest form of chemical bond.
Formed by the electrostatic attraction between ions of opposite
charge, after electrons have been transferred.
The strength of the ionic bond depends on distance between the
ions and/or the strength of the electrical charge.
Dominant bond in mineral structures - ~90%.
Covalent Bonds –
Formed between elements that share electrons (i.e., don’t readily
gain/lose electrons & form ions).
Generally stronger than ionic bonds.
E.g., Diamond – C atoms sharing 4 of its own e - ‘s w/ 4 other C’s
arranged in a 4-sided pyramidal shape (tetrahedron).
Metallic Bonds –
Atoms of metallic elements have strong tendencies to lose electrons
and pack together as cations w/ freely moving electrons
shared/dispersed between them.
A type of covalent bond.
Among a small number of minerals, incl. metal copper & some sulphides.
Some minerals have chemical bonds intermediate between pure ionic & pure covalent.
The Formation of Minerals:
Ch 3; Earth Materials: Minerals & Rocks
What are Minerals?
Mineralogy =
1. The branch of geology that studies the composition, structure, appearance, stability, occurrence, and
associations of minerals
2. The relative proportions of a rock’s constituent minerals.
Mineral = A naturally occurring, solid crystalline substance, generally inorganic, with a specific chemical
composition.
Minerals are:
Homogenous – they can’t be divided mechanically into smaller components.
Naturally occurring – Must be found in nature (e.g., Diamonds mined in S Africa are minerals, but lab
produced ones are not minerals)
Solid (1) Crystalline Substances (2) – (1) Solid substances (not liquid or gas) & (2) have atoms arranged
in orderly repeating 3D arrays.
Usually inorganic substances – exclude materials composed of organic C in plant/animal bodies.
However, they can be secreted by organisms.
Have a Specific Chemical Comp. – Uniqueness is determined by the chemical comp., & arrangement
of atoms w/in the internal structure.
Amorphous/glassy materials – those that lack an orderly internal arrangement e.g., Windowpane glass.
The Structure of Matter:
Atoms the smallest unit of an element that retains the physical/chemical properties of the element.
The Structure of Atoms:
Nucleus – the centre of the atom, containing virtually all the mass and 2 types of particles:
a) Proton - +vely charged. Atoms of the same element have the same No. of Protons.
b) Neutrons – Electrically neutral. Atoms of the same element may have differing No. of Neutrons.
Electrons - -vely charged. Negligible mass (~0). Surround the nucleus in a moving cloud. No. of Electrons = No.
of Protons so overall atomic charge = 0.
Atomic Mass & Number:
Atomic Number = The number of protons w/in the nucleus. Defines the type of element. Also, the number of
electrons.
Elements in the same Group (vertical column) tend to have similar chemical properties.
Atomic Mass = Sum of the No. of Protons & Neutrons. Atoms of the same element may have differing Atomic
Masses, resulting from differing No.’s of Neutrons (but same Protons) …
Isotope = Atoms of the same element w/ different No.’s of neutrons.
Chemical Reactions:
, Chemical Reactions = interactions of the atoms of 2 or more chemical elements in certain fixed proportions
that produce chemical compounds.
The structure of an atom determines its chemical reactions with other atoms.
Chemical compounds, such as minerals, are formed by either:
Electron Sharing = the mechanism by which a covalent bond is formed between the elements in the
chemical reaction. Or
Electron Transfers = the mechanism by which an ionic bond is formed between the elements in the
chemical reaction.
Ion = An atom or group of atoms that has an electrical charge (+/-) because of the loss/gain of 1 or more
electrons.
Cation = A positively charged ion.
Anion = A negatively charged ion.
Chemical Bonds:
When chemical compounds are formed either via electron sharing/transfer, the ions/atoms that make up the
compound are held together by electrostatic attraction between -ve electrons & +ve protons.
The attractions or chemical bonds, between shared or lost/gained electrons can be strong or weak.
Strong bonds prevent a compound from decomposing into its elements or other compounds and keep
minerals hard and from cracking/splitting.
Ionic Bonds –
The simplest form of chemical bond.
Formed by the electrostatic attraction between ions of opposite
charge, after electrons have been transferred.
The strength of the ionic bond depends on distance between the
ions and/or the strength of the electrical charge.
Dominant bond in mineral structures - ~90%.
Covalent Bonds –
Formed between elements that share electrons (i.e., don’t readily
gain/lose electrons & form ions).
Generally stronger than ionic bonds.
E.g., Diamond – C atoms sharing 4 of its own e - ‘s w/ 4 other C’s
arranged in a 4-sided pyramidal shape (tetrahedron).
Metallic Bonds –
Atoms of metallic elements have strong tendencies to lose electrons
and pack together as cations w/ freely moving electrons
shared/dispersed between them.
A type of covalent bond.
Among a small number of minerals, incl. metal copper & some sulphides.
Some minerals have chemical bonds intermediate between pure ionic & pure covalent.
The Formation of Minerals:
