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In order for a substance to be a mineral, it must have ALL five of the following characteristics:

In order for a substance to be a mineral, it must have ALL five of the following characteristics:

a.     Naturally Occurring – it must be formed by processes that occur in the natural world.                                    

I. Example:  Quartz forms naturally as magma cools and hardens deep beneath the Earth’s surface.

 ii.     Plastic, brick, glass, steel are NOT minerals because they are man-made.

    Inorganic– Cannot form from materials that were once part of a living thing.

i.     Example:  Coal is NOT a mineral because it forms from the remains of plants that lived long ago.

c.     Solid (NOT liquid).  Definite volume and shape; particles are tightly packed together so they cannot move like they can in a liquid.

i.     Water is NOT a mineral in its liquid form, but can become a mineral when it cools and hardens.


Crystal structure – the particles in the mineral line up in a pattern that repeats over and over.

i.     The repeating pattern forms a solid called a crystal

ii.     A crystal has flat sides called faces that meet at sharp edges and corners.

e.     Definite chemical composition – minerals always contains certain elements in definite proportions.

i.     Minerals can be either elements (a single substance) or a compound (a combination of 2 or more elements).

ii.     Most minerals chemically are compounds, because they are made of two or more elements.

Hardness-A mineral’s ability to scratch or be scratched by another mineral; Mohs Hardness scale; Ranked 1-10; Determined with a scratch test-minerals can only scratch a softer mineral

Color-characteristic property of some minerals; Not always reliable: i.e. quartz in different colors; physically observed by sight 

Streak-The color of a mineral’s powder; a mineral’s color may vary, but its streak does not and they are often different; Rub a mineral against a piece of unglazed tile and visually observe powder

Density-Mass per unit volume; Calculated by density=mass/volume; Mass determined using a balance and Volume determined with water displacement

Crystal System-Crystal shapes put into six groups based on number and angle of crystal faces; Visually observed using microscopes if too small to observe with the naked eye


Luster-How a mineral reflects light from its surface; Minerals containing metal are usually shiny-Terms used: earthy, waxy, pearly, glassy; visually observed

  • By evaporation – When minerals are dissolved in water, and the water evaporates, the minerals that are left behind will form crystals

Example:  Slow evaporation of seawater leaves behind minerals such as halite and calcite

  • By the cooling of a hot water solution:

Magma heats water underground     Minerals dissolve in hot water to form solutions     Solutions follow cracks in earth’s crust called veins     As solution cools, elements crystallize to form a mineral.

Example: Pure Silver can crystallize in veins from a hot water solution.

  • Minerals are formed by crystallization- process where atoms join to form a crystal structure

Crystallization of magma or lava:

Crystallization of materials dissolved in water

  • Formed when magma cools inside crust or when lava cools and hardens on the surface:

Slow cooling deep underground forms large crystals

Fast cooling close to or above the surface forms small crystals



In order for a substance to be a mineral, it must have ALL five of the following characteristics:

a.     Naturally Occurring – it must be formed by processes that occur in the natural world.                                    

I. Example:  Quartz forms naturally as magma cools and hardens deep beneath the Earth’s surface.

 ii.     Plastic, brick, glass, steel are NOT minerals because they are man-made.

    Inorganic– Cannot form from materials that were once part of a living thing.

i.     Example:  Coal is NOT a mineral because it forms from the remains of plants that lived long ago.

c.     Solid (NOT liquid).  Definite volume and shape; particles are tightly packed together so they cannot move like they can in a liquid.

i.     Water is NOT a mineral in its liquid form, but can become a mineral when it cools and hardens.


Crystal structure – the particles in the mineral line up in a pattern that repeats over and over.

i.     The repeating pattern forms a solid called a crystal

ii.     A crystal has flat sides called faces that meet at sharp edges and corners.

e.     Definite chemical composition – minerals always contains certain elements in definite proportions.

i.     Minerals can be either elements (a single substance) or a compound (a combination of 2 or more elements).

ii.     Most minerals chemically are compounds, because they are made of two or more elements.

Hardness-A mineral’s ability to scratch or be scratched by another mineral; Mohs Hardness scale; Ranked 1-10; Determined with a scratch test-minerals can only scratch a softer mineral

Color-characteristic property of some minerals; Not always reliable: i.e. quartz in different colors; physically observed by sight 

Streak-The color of a mineral’s powder; a mineral’s color may vary, but its streak does not and they are often different; Rub a mineral against a piece of unglazed tile and visually observe powder

Density-Mass per unit volume; Calculated by density=mass/volume; Mass determined using a balance and Volume determined with water displacement

Crystal System-Crystal shapes put into six groups based on number and angle of crystal faces; Visually observed using microscopes if too small to observe with the naked eye


Luster-How a mineral reflects light from its surface; Minerals containing metal are usually shiny-Terms used: earthy, waxy, pearly, glassy; visually observed

  • By evaporation – When minerals are dissolved in water, and the water evaporates, the minerals that are left behind will form crystals

Example:  Slow evaporation of seawater leaves behind minerals such as halite and calcite

  • By the cooling of a hot water solution:

Magma heats water underground     Minerals dissolve in hot water to form solutions     Solutions follow cracks in earth’s crust called veins     As solution cools, elements crystallize to form a mineral.

Example: Pure Silver can crystallize in veins from a hot water solution.

  • Minerals are formed by crystallization- process where atoms join to form a crystal structure

Crystallization of magma or lava:

Crystallization of materials dissolved in water

  • Formed when magma cools inside crust or when lava cools and hardens on the surface:

Slow cooling deep underground forms large crystals

Fast cooling close to or above the surface forms small crystals