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Minerals 4.1 – What is a mineral?

4.2 – Types of minerals.

Minerals

• A mineral is a naturally occurring inorganic solid, with a specific chemical composition, and a definite crystalline structure.

• Natural, inorganic, crystalline solid

• Basic materials of the Earth’s crust

Is it a mineral? • Minerals are naturally occurring • They are not made by humans

• Minerals are inorganic • They have never been alive and are not made

from plants or animals • Is salt a mineral? Sugar? Coal?

• Minerals are solids. • Definite shape and volume

• Is water a mineral? What about ice?

Is it a mineral?

• Minerals have a specific chemical composition. • Each one is a particular mix of chemical

elements. • Some consist of a single element: Gold, silver,

sulfur etc.

• Minerals have a definite crystalline structure. • A crystal is a solid in which atoms are arranged in

repeating patterns. • The crystals that make up minerals are arranged

in a particular way.

Pyrite Quartz

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Aquamarine Fluorite

• Of the more than 3,000 minerals found in Earth’s crust, only about 30 are common.

• These common minerals are called rock-forming minerals because they make up most of the rocks found in Earth’s crust.

How Minerals Form

1. Crystallization from Magma

• As magma cools, elements combine to form minerals.

How Minerals Form

2. Precipitation

• When water evaporates, dissolved substances react to form minerals.

• Minerals are “precipitated” out of water.

• Examples: Caves, halite, calcite

How Minerals Form

3. Pressure and Temperature

• New minerals form when existing minerals are subjected to changes in pressure and temperature.

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Identifying Minerals

•Geologists rely on several simple tests to identify a mineral.

•The tests are based on a mineral’s physical and chemical properties

Crystal Form

•Some minerals for distinctive crystal shapes.

•These shapes can be cubes, tetrahedrons, octahedrons, ect…

Pyrite Fluorite

Luster

•Luster is the way that a mineral reflects light from its surface.

•There are two types of luster:

Metallic and non-metallic

Luster

•Non-metallic luster can be described as dull, pearly, waxy, shiny, silky, or earthy

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Hardness

•Hardness is one of the most useful and reliable tests for identifying minerals.

•German geologist Friedrich Mohs developed a scale by which hardness can be determined.

Hardness

•Hardness is a measure of how easily a mineral can be scratched.

•The Mohs Scale of Hardness is used as a reference to determine the hardness of a material.

Cleavage and Fracture

•A mineral that splits relatively easily and evenly along one or more flat planes is said to have cleavage.

•Mica is an example of a mineral with 100% cleavage in one plane.

100% Cleav. 1 direction Cleavage and Fracture

•Minerals that break apart with rough or jagged edges are said to have fracture.

• Flint, jasper, and quartz are some examples of minerals that exhibit fracture.

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Fracture Streak

• Streak is the color of a mineral when it is broken up and powdered.

• The streak test is performed by rubbing a mineral across an unglazed porcelain plate.

Color

•One of the most noticeable characteristics of a mineral is its color.

•Color is sometimes caused by the presents of trace elements or compounds within a mineral (iron, nitrogen, titanium)

Density and Specific Gravity •Density is expressed as the mass

of an object divided by its

volume: 𝑫 =𝑴

𝑽

•𝑫𝒆𝒏𝒔𝒊𝒕𝒚 =𝑴𝒂𝒔𝒔

𝑽𝒐𝒍𝒖𝒎𝒆

Density

•Density is expressed as the mass of an object divided by its

volume: 𝑫 =𝑴

𝑽

•𝑫𝒆𝒏𝒔𝒊𝒕𝒚 =𝑴𝒂𝒔𝒔

𝑽𝒐𝒍𝒖𝒎𝒆

Specific Gravity

Specific gravity is the ratio of the mass of a substance to the mass of water

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Calculate

•𝐷𝑒𝑛𝑠𝑖𝑡𝑦 = 𝑀𝑎𝑠𝑠

𝑉𝑜𝑙𝑢𝑚𝑒

•D = 𝑴

𝑽

•Gold has a density of 19.3g/cm3

•Calculate the volume of a 5g sample of gold.

Minerals

• A mineral is a naturally occurring inorganic solid, with a specific chemical composition, and a definite crystalline structure.

• Natural, inorganic, crystalline solid

• Basic materials of the Earth’s crust

What is a Crystal?

•A crystal is a solid in which the atoms are arranged in repeating pattern

•Ex: Diamond crystalline structure

Properties of Minerals

•Luster

•Hardness

•Cleavage

•Fracture

•Streak

•Specific Gravity (Density)

Section 4.2: Types of Minerals •Everything on Earth is classified into

categories.

•Ex: food, music, animals…

•Minerals are also classified into groups based on their chemical compositions.

•Silicates, Carbonates, Oxides, Sulfides, ect…

Silicates:

•Oxygen is the most abundant element in Earth’s crust, followed by silicon.

•Minerals that contain silicon and oxygen atoms are known as silicates.

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Silicates Continued:

•Silicates make up around 96% of the minerals present in Earth’s crust.

•Feldspar and quartz are the most common silicates.

•KAlSi3O8 SiO2

Silicates:

Silica Tetrahedron • The basic building block of the

silicates is the silica tetrahedron.

•A tetrahedron is a geometric solid having four sides that are equilateral triangles, resembling a pyramid.

• Tetrahedra can combine in many ways giving silicates many different properties.

Silica Tetrahedron

Carbonates: • Carbonates are minerals composed of

one or more metallic elements and the carbonate ion CO3

2-

• Examples of carbonates are calcite, dolomite, and rhodochrosite.

• Carbonates are the primary minerals that make up limestone and marble.

• Carbonates can react with acid.

Oxides: • Oxides are composed of oxygen and a

metal.

• Hematite (FE2O3) is a common iron oxide and a good source of iron.

• Uraninite (UO2) is valuable because it is the major source or uranium used to generate nuclear power.

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Other Groups: • Sulfides, sulfates, and halides, are other

major mineral groups

• They are elements containing sulfer, sulfate ions, or chloride or fluoride along with sodium or potassium. (salts)

• A native element is a mineral made up of one element only.

• Ex: Native Silver (Ag), Native Copper (Cu)

Economic Minerals: • Minerals are virtually everywhere.

• Used to make computers, cars, TV’s, desks, roads, buildings, jewelry, paints, medicines…

• The value and uses of minerals can change over time.

• During the War of 1812, salt brine was used to pay soldiers in the field.

Ores: • An ore is a type of rock that contains

minerals with important elements including metals.

• The ores are mined and then refined to extract the valuable element or elements.

• Ex: Hematite is an ore that contains the element iron.

Open-Pit Mining:

Open-Pit Mining:

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Gems: • Gems are valuable minerals that are

prized for their rarity and beauty.

• They are very hard compared to most other elements (scratch resistant)

• The presence of trace elements can make one variety of mineral more colorful and more valuable

• Ex: Quartz & Amethyst