MINERALS
Characteristics
Criteria
Solid
Naturally occurring
In-organic
Fixed chemical formula
Crystal structure
All the physical properties of a mineral result from the mineral's internal arrangement of atoms.
Formation
Minerals form as the magma and lava cools from a liquid to a solid state.
Magma is molten material from inside Earth that hardens to form rock.
Lava is magma that reaches the Earth surface. Lava also forms rock when it cools and hardens.
Crystalization
Sometimes the elements and compounds that form minerals are dissolved in water to form solutions.
A solution is a mixture in which one substance is dissolved in another.
When elements and compounds that are dissolved in water leave a solution, crystallization occurs.
Crystallization is the process by which Minerals can form in this way underground and in the bodies of water on the Earth’s surface. where the atoms are arranged in repeating patterns.
Minerals can form in this way underground and in the bodies of water on the Earth’s surface.
Crystal structure greatly influences a mineral’s physical properties.
A mineral must be a solid, with a definite shape and volume. A substance that is a liquid or gas is not a mineral.
To be classified as a mineral, a substance must be formed by processes of the natural world.
This means that the mineral can’t form from materials that were once part of a living thing.
Every mineral is an element or compound with a chemical composition that is unique to that mineral.
The particles of a mineral form a pattern that repeats over and over again. The orderly, repeating, three–dimensional pattern of a mineral’s particles forms a solid called a crystal.
Physical properties
Luster
Hardness
Color
Streak
Cleavage
Fracture
Specific gravity
Crystal system
Special properties
Metallic: bright, shiny, reflective
The way a surface reflects light
Submetallic: dull, reflective
Non–metallic: dull
A mineral’s resistance to being scratched, is used to determine how hard a mineral is
Mohs scale: Hardness ranges from 1 (soft) to 10 (hard).
A mineral that is higher in number on the scale will scratch anything that has a lower number.
The color of a mineral is an easily observed physical property.
The same mineral can come in a variety of colors.
This is the color of the dust that is left after you grind up a mineral.
Rubbing the mineral on the ceramic streak plate, which has a hardness of 7. Any mineral that is softer than 7 will leave a little dust on the plate when it is rubbed on it.
Cleavage is how a mineral splits or breaks.
The mineral does the same split every time.
When a mineral shatters, it doesn’t always break evenly like cleavage.
It fractures into different shapes depending on what mineral it is. Some have jagged edges, some have smooth ones, and some break into grains or uneven chunks.
This is the weight of the mineral compared to the weight of water. This tells the scientist how heavy or dense a mineral is.
There are six major crystal systems. A mineral always has the same one.
Some properties are particular to only a few types of minerals. These unique properties can help you quickly identify the minerals.
Compostions
Elements make up 98% Earth's crust: oxygen (46.6%), silicon (27.7%), sodium, potassium, magnesium.
There are 12 common rock–forming minerals that are composed almost completely of these eight elements. Most of the rock–forming minerals are silicates. All minerals are classified by their compositions.
The largest group of minerals is the silicates. Silicate minerals contain silicon and oxygen and one or more other elements.
Minerals that do not contain a combination of the elements silicon and oxygen form a group called the nonsilicate minerals.
Major groups of nonsilicate minerals are carbonates, oxides, sulfides, halides, sulfates, and native elements.
The second most common group of rock–forming minerals is the carbonates. All the minerals in this group contain carbon and oxygen joined together.
Identify minerals
Using the hardness of common objects such as a fingernail, copper penny, iron nail, glass plate, steel file, and a streak plate you can determine an unknown mineral’s hardness by doing a scratch test.
Utilizing your own sense of sight, touch, and smell you can evaluate an unknown mineral’s color, luster, feel, and smell.
Some minerals have special properties that are unique to just a few minerals. If you can locate a special property, it greatly assists in identifying it.