Minerals

Question 1

What are minerals?

Answer 1

Inorganic, naturally occurring solids. They are crystalline substances with characteristic internal structure, and chemical compositions that are either fixed, or vary within fixed limits.

Question 2

What are some organic materials?

Answer 2

Vegetation, coal, oil, and gas are all derived from strictly organic sources. Therefore, none of these are minerals.

Question 3

Many organisms do what that allow them to count as minerals?

Answer 3

They secrete/metabolize shells and hard parts that are identical to true minerals that can also be produced by inorganic processes.

Question 4

Inorganic does NOT mean…

Answer 4

has no carbon (e.g. diamonds and graphite) even though earth has carbon-based life forms.

Question 5

Are synthetic compounds minerals even if they conform to the definition?

Answer 5

No, even if synthetic compounds conform to the definition in every way, they don’t count because they are not naturally occurring.

Question 6

Can liquids or gases be minerals?

Answer 6

No, minerals must be solids at atmospheric temperature and pressure. However, water in the form of ice does count as a mineral.

Question 7

What does having a crystalline structure imply?

Answer 7

That the mineral has a consistent, repeating, internal arrangement of atoms.

Question 8

Why isn’t glass a mineral?

Answer 8

Because glass has no ordered arrangement of atoms and is therefore amorphous (lacking a clear structure).
A-(without)-morphous-(shape).

Question 9

How are minerals fixed or vary within fixed limits?

Answer 9

Some minerals have fixed chemical compositions (quartz, SiO2, and calcite, CaCO3) whereas others vary due to ionic substitution (plagioclase feldspar and olivine).

Question 10

Minerals are nothing more than _______ that conform to their definition

Answer 10

chemical compounds

Question 11

What things are bonded to make stable chemical compounds?

Answer 11

Atoms, ions, ion groups and molecules.

Question 12

What are some interparticle bond types?

Answer 12

Ionic bonds, covalent bonds, and van der Waal’s or residual bonds

Question 13

How is a cation formed?

Answer 13

When atoms of an element give up one of more electrons to become positively charged.

Question 14

How is an anion formed?

Answer 14

When electrons are accepted by an element to become negatively charged.

Question 15

How is an ionic bond formed?

Answer 15

When cations and anions are connected by a strong electrochemical bond; both the cation and anion achieve a stable elcetron configuration. E.g. NaCl

Question 16

A greater variety of minerals use _____ bonds more than any other type.

Answer 16

Ionic

Question 17

How are covalent bonds formed?

Answer 17

When electrons are shared between atoms (may be of the same or different element) to achieve a stable electron configuration.

Question 18

How are the bonds in a diamond different from the bonds in graphite?

Answer 18

In a diamond, each C is single-bonded to 4 other C atoms whereas in graphite, at a different pressure and temperature, each C is bonded to 3 other C atoms in alternating single and double bonds (like a benzene ring) to produce sheets bonded to each other with van der Waal’s bonds.

Question 19

How are van der Waal’s/ residual bonds formed?

Answer 19

Electrical asymmetry of bonded atoms and molecules produce weak residual surface charges; these are weak bonds that are easily broken, think of graphite on paper.

Question 20

What is the name for different minerals, such as diamonds and graphite that have the same chemical composition but different crystalline structures?

Answer 20

Polymorphs.

Poly-(many)-morphs-(forms).

Question 21

Minerals are crystalline by virtue of what characteristic?

Answer 21

Their ordered internal arrangement of atoms, not by their external form.

Question 22

What causes imperfections on minerals?

Answer 22

Mutual interference, flaws caused by growth irregularities (think of tetris), and impurities.

Question 23

What is a unit cell?

Answer 23

The minimum repeating structural entity within the structure; usually on the order of a few to less than 20 A

Question 24

Why are crystals variable in shape?

Answer 24

Because the crystal grows by addition of unit cells to the lattice at variable rates in different directions, therefore, crystals aren’t just exact copies of each other.

Question 25

The regular structure and electron configuration of crystals give chemical stability and may allow…

Answer 25

atoms of two elements of similar size and charge to substitute for each other in the structure/lattice (they both “fit”).

Question 26

An example of a mineral with a variable within fixed limits is…
Also, what is the term for this type of variable within fixed limits?

Answer 26

Olivine which may have either magnesium, iron, or any mixture of the two as its cation in its chemical composition. This is called solid solution (a range of compositions).

Question 27

What allows us to identify minerals?

Answer 27

The combination of chemical compositions and crystal structures which is characteristic of each mineral.

Question 28

How is hardness of minerals measured?

Answer 28

Using Mohs Hardness Scale (know). It is only a relative scale, it’s not linear or logarithmic.

Question 29

What is cleavage?

Answer 29

Cleavage exists if there are directions or planes of weakness in the crystal structure of a mineral. A single cleavage repeats several times in a single crystal. Many minerals have 2 or more cleavages (feldspar, calcite) whereas some minerals have none (quartz).