Mineral Overview

Question 1

Mineral

Answer 1

A mineral is a naturally occurring, inorganic substance that has a more or less definite chemical composition (expressed as a chemical formula), and an orderly arrangement of its constituent atoms into a definite three dimensional arrangement.

Question 2

How do minerals form?

Answer 2

as a result of the crystallization of a solution, melt or gas.

Question 3

what determines most of the physical properties in a mineral?

Answer 3

the crystal structure

Question 4

What is a crystal structure?

Answer 4

the definite three-dimensional arrangement of atoms within a mineral that repeats itself continuously.

Question 5

why do we distinguish between physical properties of minerals?

Answer 5

because the physical properties are used to identify a mineral

Question 6

list the physical properties used to identify minerals

Answer 6

• Color
• streak
• Lustre
• Habit
• cleavage/fracture
• Hardness
• Tenacity
• Magnetism
• Smell/Taste/Touch
• Specific gravity/density

Question 7

Color

Answer 7

color is the most obvious feature and is frequently related to chemical composition or impurities in the mineral(color is not always a diagnostic, e.g. Quartz is colorless when pure but can be encountered as the following varieties:

• black - Smokey Quartz
• Pink - Rose Quartz

Question 8

Streak

Answer 8

streak is the color shown by the mineral in a finely powdered form when rubbed on a piece of unglazed porcelain and is often diagnostic.

Some minerals are superficially very similar, e.g. Pyrite and Gold may be mistaken for one another based on their lustre and color. However, both minerals have unique streaks.

pyrite - Greenish-black streak
Gold - Gold-yellow streak

Question 9

Lustre

Answer 9

The lustre is the surface appearance as it reflects light and varies from metallic to non-metallic.

Question 10

Habit

Answer 10

The 3d arrangement within a crystal. there are a number of ways in which a crystal’s atoms can be arranged. some examples are:

• Cube
• Octahedron
• Rhombododecahedron
• Prisms
• Pyramids
• Pinacoids
• Rhombohedron

Question 11

Cleavage

Answer 11

When the break forms flat surfaces that are parallel to crystal directions, mimics the crystal structure.
the tendency to break into smaller pieces (crystals) with the identical shape as the original piece.

Question 12

Fracture

Answer 12

Fracture is the tendency to break with an irregular, uneven surface.

Question 13

Hardness

Answer 13

the resistance to being scratched. Ten well-known minerals are arranged in order of increasing hardness into Mohs hardness scale. An unknown mineral is given a hardness value by testing and comparison to those on the Mohs scale.

Question 14

What is a rock?

Answer 14

A rock is a naturally occurring, multi-granular aggregate of minerals, and consists of crystals of one or more kinds of mineral.

Question 15

What are rock-forming minerals?

Answer 15

Rock-forming minerals are mostly silicates. Silicates contain the elements silicon [Si] and oxygen [O].

Question 16

Salic minerals

Answer 16

Light/colorless minerals with low density. ( silica (quartz) and aluminium silicates are prominent )

Typical mineral families are:

3. Quartz
4. Feldspars
5. Feldspathoids

these minerals are abundant in acidic igneous rocks

Question 17

Femic(Mafic) Minerals are:

Answer 17

Dark minerals with a high density. ( Magnesium and Iron are usually prominent ) 
Typical mineral families are:
1. Pyroxenes
2. Amphiboles
3. Micas
4. Ca-Feldspars
5. Olivines

Question 18

List the properties of minerals related to crystal form

Answer 18

Habit, cleavage, fracture, and hardness

Question 19

Describe what is meant by the prismatic crystal habit mineral crystals

Answer 19

consist of three to six faces in parallel pairs

Question 20

Crystal form of Garnet

Answer 20

Dodecahedron

Question 21

Crystal form of Calcite

Answer 21

Rhombohedron

Question 22

what cleavage does Galena have?

Answer 22

Cubic

Question 23

what cleavage does Calcite have?

Answer 23

Rhombohedral