Variety of Minerals

4.1  Variety of Minerals

 

Definition

Minerals are natural substances that have a fixed chemical composition and are usually found in rocks that exist in the form of elements or compounds

 

  • Minerals that exist in the elemental form are usually inactive and unresponsive

  • Examples of natural mineral elements are divided into metallic elements (gold, silver, mercury, and platinum) and non -metallic elements (carbon and sulfur)

The elements that make up natural compounds:

  • The elements that combine with other elements such as oxygen and sulfur will form compounds and become more stable

The physical properties:

  • Minerals have different colors and hardness, depending on their chemical composition

Minerals

Color

Hematite

Brown

Malakite

Green

Calcite (limestone)

White

Galena

Gray

Cassiterite

Black

 

  • Mineral hardness can be determined by scratching or using a sclerometer

  • Less hard minerals are easier to scratch than harder minerals

  • Mineral hardness is measured in Mohs scale, calcite scale 3 while diamond scale 10 (hardest)

The chemical properties:

  • Most minerals are insoluble in water except those containing the metal elements sodium and potassium

  • Minerals containing metal oxides or metal carbonates react, dissolve with acids, and release carbon dioxide gas

  • Minerals containing metal oxides are more stable and do not decompose when heated but produce pure metals and carbon dioxide gas when heated with carbon

  • Minerals containing metal carbonate will decompose when heated and produce metal oxides and carbon dioxide gas except sodium carbonate and potassium carbonate

  • The carbon dioxide gas released will cloud the lime water

  • Metal sulfides decompose when heated in air to produce metal oxides and sulfur dioxide gas

  • The resulting sulfur dioxide gas has a strong odor and turns purple in an acidic solution of potassium permanganate

Uses of natural minerals:

  • Calcium oxide and calcium carbonate (limestone) are used to neutralize acidic soils

  • Calcium carbonate is also used in blast furnaces to isolate impurities during iron extraction

  • Silicon dioxide (or silica) found in sand has a high melting point (about 1,713 ° C) and is used to make glass

  • Aluminum oxide is commonly found in sunscreens and in cosmetic materials such as nail polish and lipstick

Example question:

The element aluminium is commonly found in the earth's crust in the form of aluminium oxide compounds found in bauxited.

However, the element of gold is usually found in the for of pure gold.

Briefly explain the statement.

Answer:

Aluminium is a reactive element then aluminium combines with oxygen to form a more stable aluminium oxide.

Gold is a very non-reactive element and therefore gold does not combine with other elements and exists as a independent element.