Minerals - section 3.pdf

Minerals Earth and Space Science Defining a Mineral • A mineral is a naturally occurring inorganic solid, with a definite chemical composition, and an ordered atomic arrangement. Breaking down the definition • Minerals are naturally occurring…………………..They are not made by humans • Minerals are...

Minerals Earth and Space Science Defining a Mineral • A mineral is a naturally occurring inorganic solid, with a definite chemical composition, and an ordered atomic arrangement. Breaking down the definition • Minerals are naturally occurring…………………..They are not made by humans • Minerals are inorganic…..They have never been alive and are not made up from plants or animals • Minerals are solids………….They are not liquids (like water), or gases (like the air around you) • Minerals have a definite chemical composition They have a formula • Minerals have an ordered atomic arrangement…..The chemical elements that make up each mineral are arranged in a particular way - this is why minerals 'grow' as crystals 1. Colour – Some minerals are always the same colour. Malachite and azurite are both copper minerals. Malachite and azurite can be found together, but malachite is always green, azurite blue 1. Colour – But many minerals can be a variety of colours. Fluorite for instance can be lots of different colours. The different colours are caused by the slight imperfections or impurities a mineral may contain. To identify many minerals you must look at more than just their colour. 2. Lustre Luster refers to the way the mineral reflects light Eg. Glassy – reflects light like a piece of glass Metallic – reflects light like a piece of metal Dull – does not reflect light well And others… 3. Streak – The streak of a mineral is the color of the powder produced when it is dragged across a surface. The color could be different from the minerals color, and is always distinctive Many minerals do not have a streak 4. Hardness • Hardness is the resistance of a mineral to scratching. • It is a property by which minerals may be described relative to a standard scale of 10 minerals. This is known as the Mohs scale of hardness. Mohs scale of hardness • In 1812, Friedrich Mohs – famous geologist and mineralogist created a scale of mineral hardness grading from the softest (1) to the hardest (10). The scale was created using the simple technique of one mineral's ability to visibly scratch another Moh’s Hardness Scale 6. Mineral Cleavage – Cleavage is the way a mineral breaks/splits along definite crystallographic structural planes. Cleavage can be in one plane or multiple planes. 7. Fracture Fracture is the property of a mineral breaking in a more or less random pattern. Minerals with no cleavage generally break with irregular fracture called a concoidal fracture