Earth Science - Physical and Chemical Properties of Minerals

Minerals

Is a naturally occurring, inorganic solid with a definite chemical composition and an orderly internal atomic structure (meaning it’s crystalline)

• Naturally Occurring

• Inorganic

• Homogenous Solid

• Definite Chemical Composition

• Ordered Internal Structure (Crystalline)

Characteristics of Minerals

Naturally Occuring

• It must be formed by natural geological processes, not created by humans in a lab

• It should be made by natural processes without the aid of any organism

Inorganic

• It generally does not come from living organisms or the products of organic life

• This would mean that bones, shells, and other hard parts of a living organism are not miners

Homogenous Solid

• It must exist in a solid state at normal Earth surface temperatures and pressures

• We should be able to see something uniform in appearance and be in the solid state matter

Definite Chemical Composition

It has a specific chemical formula that varies only within defined limits

Ordered Internal Structure (Crystalline)

• Its atoms are arranged in a systematic, repeating pattern, forming a crystal lattice

• This internal order often results in distinct crystal shapes when the mineral has space to grow

• Crystal Habit

• Luster

• Cleavage and Fracture

• Hardness

• Color

• Streak

• Tenacity

Distinguish the Physical Appearance:

• Magnetism

• Striations

• Specific Gravity

• Taste, Odor, Feel

Additional Properties (minerals):

Crystal Habit

• Refers to the overall shape or growth pattern of the mineral. It can be described as equant, elongate, and platy

• Equant

• Elongate

• Platy

Crystal Habits:

Equant

Three dimensions of the mineral have about the same length, like that of a cube or sphere

Elongate

Forms prismatic of prism-like crystals that are thicker than the needle as in a pencil

Platy

Looks like a flattened and thin crystal (like plate)

Garnet

Example of equant

Indicolite

Example of Elongate

Wulfenite

Example of Platy

Luster

Describes the appearance of a mineral when light is reflected from its surface

• Opaque

• Translucent

• Transparent

Luster:

Opaque

When light strikes, the object does not pass through

Translucent

When light strikes the object, and some light passes through

Transparent

When light strikes and almost all the light will completely pass through

Cleavage

refers to the tendency of minerals to break along very smooth, flat, and shiny surfaces

Fracture

Mineral breaks randomly leaving jagged surface

Hardness

The resistance of a mineral to scratching, measured by scratching the mineral against another substance of known ______

Friedrich Mohs

To determine the hardness of a mineral, a comparative hardness scale assigning numerical values to the hardness was made by ____________________

• Tale

• Gypsum

• Calcite

• Fluorite

• Apatite

• Feldspar

• Quartz

• Topaz

• Corundum

• Diamond

Mohs Scale of Mineral Hardness: 1-10

Color

• One of them most obvious properties of a mineral but not reliable alone

Streak

Refers to the color of the fine powder of a mineral usually obtained by rubbing the mineral on an unglazed, porcelain streak plate

Tenacity

Describes the minerals reaction to stress

Sectility

Ability of minerals to be sliced by a knife

Magnetism

Some minerals are attracted to a hand magnet

Striation

Presence of very thin, parallel grooves

Specific GRavity

Is the weight of that mineral divided by the weight of an equal volume of water

Taste, Odor, Feel

Chemical Properties

• Show the presence and arrangement of atoms in minerals

• Identified by how they react to certain substances

1. Native Elements

2. Silicates

3. Oxides

4. Sulfides

5. Sulfates

6. Halides

7. Carbonates

8. Phosphates

9. Mineraloid

Classification of Minerals:

Native Elements

• These minerals are naturally occurring in nature in an uncombined form with a distinct mineral structure

• It can be classified as metals, semimetals, nonmetals

Silicates

• this is the largest group of minerals

• it contains silicon and oxygen, with some aluminum, magnesium, iron, and calcium

Feldspar

Example of an Silicate:

Oxides

It is formed from the combination of a metal with oxygen. This group ranges from dull ores like bauxite to gems like rubies and sapphires

• Magnetite

• Bauxite

Example of an Oxide:

Sulfides

• these are made of compounds of sulfur usually with a metal

• They tend to be heavy and brittle

Pyrite

Example of an Sulfide:

Sulfates

• These are made of compounds of sulfur combined with metals and oxygen

• It is a large group of minerals that tend to be soft and translucent

Gypsum

Example of an Sulfate:

Halides

• They form from halogen elements like chlorine, bromine, fluorine and iodine combined with metallic elements

• They are very soft and easily dissolved in water

Halite

Example of an Halide:

Carbonates

• These are group of minerals made of carbon, oxygen, and a metallic element

• Among the most widely distributed minerals in the Earth’s crust

Dolomite

Example of an Carbonate:

Phosphates

They are often formed when other minerals are broken down by weathering. They are often brightly colored

Mineraloid

• It is the term used for those substances that do not fit neatly into one of the eight classes

• It is a mineral-like substance, but it does not meet the criteria to be a mineral

• It doesn’t have a crystallin structure

Amber

Example of an Mineraloid: