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Chapter 9 : Rocks and Minerals Section 1: Minerals—Earth’s Jewels

**Definition of Minerals Minerals are: naturally occurring, inorganic, solid materials, with a definite chemical composition and a crystalline internal arrangement. Definite chemical composition means: the atoms that make up the mineral will always be the same ones and in the same proportion.

*Minerals are Crystalline Solids Crystals are solid materials with atoms arranged in repeating patterns Minerals have this repeating pattern.

********Crystallization is the (natural or artificial) process by which a solid forms and in this solid, the atoms or molecules are organized in a repeating pattern known as a crystal.

Different types of internal structure

The surfaces of minerals show the repeating crystalline pattern

IMPORTANT ****The definition of mineral highlights very important characteristics of minerals:

**Important characteristics of minerals 1)formed by natural processes – not man made 2)Minerals are inorganic – can’t come from plants or animals 3)Minerals have a definite chemical composition – formed always by the same types of chemical elements (periodic table) 4) Minerals are crystalline solids If a material does not have the characteristics above, it is not a mineral


Rocks x Minerals

Rocks are usually made of two or more minerals. MINERALS are considered the building blocks of rocks and their presence help identify the rock.

How do Minerals form? 4 processes 1) from magma 2) from lava 3) In processes that involve evaporation of liquids 4) In processes that involve precipitation of solids (crystallization)

1) From magma - melted rock that is inside the Earth will cool and form minerals inside the Earth. 2) From lava - magma that reaches the Earth’s surface will cool and form minerals on the Earth’s surface

How do minerals form? 2 more processes 3) Precipitation – when there is too much dissolved materials in water, the excess can precipitate and form crystals 4) Evaporation - salt and other minerals can crystallize when sea water evaporates

• The size of the crystals is a clue that tells us if the mineral is formed from lava or magma. • Cools fast - crystals are small, formed from lava, in open air • Cools slow – crystals are bigger, formed from magma, inside the Earth. It is a slower process, crystals have more time to form. • Big crystals are also a clue that shows that the mineral had plenty of space to form.

Gems: • are minerals that are rare and can be cut and polished, giving them a beautiful appearance. • Very expensive because they are rare • Ideal for jewelry

**Geodes are holes in rocks that have crystals around the inside

Ores – are combinations of rocks and minerals • This combination of rocks and minerals is considered an ore only if: • contains enough of a useful substance that can be sold for a profit. • the ore must be extracted from Earth in a process called mining and then purified to obtain the valuable substance

Examples of Ores: • steel comes from iron that is extracted from the mineral hematite • lead for batteries is produced from the mineral galena • magnesium used in vitamins comes from the mineral dolomite.

Earth Minerals are considered non-renewable resources. Non-renewable resources are the ones that can’t be recreated by nature, once the stocks on Earth are totally used. • It takes millions of years to form minerals This is why we need to be careful when exploiting these resources.

The environmental impact also has to be taken into consideration, since many areas end up destroyed due to mining. The destruction of the environment affects plants, animals and human beings.

• It is important to recycle all materials obtained from minerals to protect the natural stocks and the environment, as well and all the organisms that inhabit the areas affected by mining and other types of exploitation

• Many of the items used in our homes and in the industry are made of minerals that were mined from the ground. • It is estimated that every person in the USA will use more than a million pounds of rocks, minerals and metals during their lifetime.