Requirements for a material to be considered a mineral
Naturally-occurring
Inorganic
Homogeneous solid
Has definite chemical composition
Ordered crystalline structure
Man-made materials such as synthetic diamonds cannot be considered real minerals.
Naturally-occurring
Organic materials such as pearls or sugar are not minerals.
Inorganic
Water is not a mineral, whereas ice is considered a mineral. Mercury occurs as a liquid in its natural state and is regarded as a mineraloid.
You should be able to describe a mineral's composition using a chemical formula.
Has definite chemical composition
Atoms in a mineral are placed in a repetitive and orderly manner. Substances that lack this kind of atomic structure, such as obsidian (volcanic glass) or plastic, are not considered minerals.
Ordered crystalline structure
Most commonly used properties in describing a mineral's appearance:
Color
Luster
Crystal Habit or Shape
Streak
Hardness
Cleavage or Fracture
Density or Specific gravity
Tenacity
Diaphaneity
Magnetism
Effervescence
Odor and Taste
The wavelengths of light reflected by the mineral.
Color
While color can be tempting to identify a mineral, it is the least valuable property because many minerals can occur in different colors
How light is reflected from the mineral's surface.
Luster
The shape of each crystal or an aggregate of crystals.
Crystal habit or shape
The color of the mineral when it is powdered
Streak
How resistant a mineral is to scratching.
Hardness
A tool used to describe a mineral's hardness relative to other mineral.
Mohs' Hardness Scale
The tendency of a mineral to break along preferred planes called zones of weakness.
Cleavage
Produced if a mineral doesn't break along zones of weakness.
Fracture
The ratio between a mineral's weight and the weight of a specific volume of water (Water has a specific gravity of 1).
Density or Specific Gravity
Heavy minerals
gold
platinum
Light minerals
graphite
How well a mineral handles stress, such as breaking, crushing, bending, or tearing.
Tenacity
How well light travels through a mineral.
Diaphaneity
The magnetic property of a mineral.
Magnetism
Moderately and weakly magnetic minerals
chromite
ilmenite
columbite
A mineral's reaction to a strong acid such as HCl (hydrochloric acid).
Effervescence
Identifying minerals by licking or smelling them.
Odor and Taste
Minerals with "rotten egg" smell
Sulfur
Pyrite
Only a few of these minerals are abundant on the Earth’s crust, called rock-forming minerals.
The other less abundant mineral group, called non-silicates, is further subdivided into groups based on their dominant anion or anionic group.
Since oxygen and silicon are the two most abundant blocks, the most common mineral group silicates uses these elements as their “building blocks.”