1. Characteristics and Properties
MINERALS
Characteristics and Properties

2. Mineral Characteristics
What is a mineral?
Naturally occurring
Not man-made (synthetic) or biologically produced.
Inorganic
Not formed from processes involving organisms (living or once living)
Solid
Has definite chemical composition
An element or compound
Has an orderly arrangement of atoms
Crystalline structure-that is-atoms have repetitive patterns and internal structures are distinct.
Geometric solids with smooth surfaces (crystal faces)

3. Formation of Minerals How are minerals formed?
One way is the cooling of magma
Thermal energy is lost; atoms migrate together and form different compounds
The elements present and the amounts determine the kind of minerals
Different crystal structures are formed
Slow or quick cooling can determine the type of minerals formed.

4. Formation of Minerals --Minerals can precipitate out of a solution
When water is saturated with dissolved solids and can’t hold any more, the excess falls out of the solution. An example of this is the manganese nodules on the ocean floor
--Minerals can form by evaporation
Minerals such as salt, gypsum and calcite (calcite forms in two ways) are formed from sea water when it evaporates. This happens in warmer parts of the world where the sun's heat evaporates the water and leaves the minerals.

5. Formation of Minerals Other ways that minerals are formed:
Some minerals are formed from the weathering of rocks.
Chemical changes are caused by atmospheric oxygen, water and acid rain. Such action can change feldspars to kaolin and pyrite (fools gold) into a brown iron ore called limonite
And lastly some minerals are formed when rocks are metamorphosed, that is subjected to heat and pressure.
Minerals formed in this way include garnet and mica.

6. Mineral Groups
Minerals that contain oxygen and silicon are called “silicates”. These two minerals combine to form most of the minerals in the earth’s crust.
They are the most abundant single minerals in the earth’s crust (oxygen-46.6%; silicon-27.7%)
More than half of the minerals in the earth’s crust are feldspars which is a silicate
Some other examples of silicates include: talc, quartz, mica, topaz, hornblende, garnet, zircon

7. Uses of Minerals Gems Rarity and beauty makes them valuable
Gemstones used for jewelry are cut and polished and sometimes don’t resemble the raw form of the mineral
May have a crystal structure that allows it to be cut in facets
May have the addition of another mineral that gives it a brighter color

8. Uses of Minerals
Ores
A mineral is an ore if it contains a substance that can be sold for profit
Hematite is the ore of iron
Bauxite is the ore of aluminum
Copper comes from chalcopyrite ore
Rutile is the ore that titanium comes from
Ore deposits are formed when fluids travel through weaknesses in rocks, such as fractures and cracks.
The minerals dissolved in the fluids are left behind when the liquid evaporates, forming “vein deposits

9. Uses of Minerals Mining
Ores are only profitable if the cost of mining them is less than the value of the material being mined
Waste rock has to be removed
This can be expensive and harmful to the environment

10. Mineral Characteristics
Identifying Characteristics of Minerals
Color
Color by itself IS NOT sufficient to identify a mineral
Luster
How the material reflects light
Metallic-shiny. Ex: silver, copper, etc
Hardness
How easily the mineral can be scratched
Can be compared to the hardness of other minerals by using the Moh’s scale
Streak
The powder form of the mineral left on a porcelain plate (must be softer than the porcelain)
Cleavage
The way the mineral splits along flat surfaces
Determined by the arrangement of the atoms
Not all minerals have cleavage
Density
Ratio of mass to volume

11. Physical Appearance
Color cannot be used exclusively to identify minerals. For example the color of turquoise can vary from blue to green
Minerals may have varying degrees of transparency, which is the ability of light to pass through a substance—quartz can be transparent, but can contain flaws that make it translucent. This is related to Luster.
Luster is definitely an identifying physical characteristic
It describes how light reflects from the surface of the mineral. Describers might include:
Metallic, waxy, pearly, earthy, dull,
glassy (vitreous), silky

12. Hardness
This is how easily a mineral can be scratched and is definitely an identifying characteristics. In order to be scratched by an object, the mineral must be softer than the object doing the scratching.
The Moh’s scale is a system of comparing the hardness of a list of 10 minerals.
Developed by Frederich Mohs
It lists them in order from 1 (softest) to 10 (hard)
It gives a list of common objects and their hardness

14. Streak Streak is the color of the powder form of the mineral
A streak plate is used to do this test. It is a piece of unglazed porcelain—which has a hardness of 7 on the Moh’s scale. A streak of the mineral is left on the porcelain when it is rubbed across with the mineral. The mineral must be softer than the streak plate if this is to work.
Some minerals leave a certain color streak, which is an identifying characteristic.
An example of this is hematite, which although it is a black mineral, leaves a red streak

15. Cleavage and Fracture
When a mineral breaks it does so either by fracturing or by cleaving. Crystal cleavage is a smooth break producing what appears to be a flat crystal face. Here are a few rules about cleavage. First cleavage is reproducible, meaning that a crystal can be broken along the same parallel plane over and over again. All cleavage must parallel a possible crystal face.
Fracture describes the way a mineral breaks and is different from cleavage. A fracture might be splintery, conchoidal (like glass) , jagged or earthy (like a ball of clay)