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Download Elements and Minerals - the Department of Earth Sciences
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Elements and Minerals Elements and Minerals The basic building blocks of landforms • Elements are substances that cannot be broken down into more elementary substances OR • They are substances of which all the atoms have the same atomic number • There are103 known elements in the Periodic Table Periodic Table of Elements Most abundant elements in the crust (From: Strahler, A & Strahler, A 2002: Physical Geography: Science and Systems of the Human Environment (2nd Ed). John Wiley & Sons, NY. Fig12.1) 1 Minerals Minerals (cont.) • The mentioned elements combine in specific ways to form minerals • So how do we define a mineral? • Minerals are homogeneous, naturally occurring, solid, inorganic substances with a definite chemical composition and a characteristic atomic structure. Examples – Quartz, Orthoclase, Biotite ect. • Let’s look at the above definition in more detail • What does “homogeneous”mean? • It means minerals are the same through and through. • They cannot be broken down into simpler components • Smashing a mineral with a hammer will result in tiny fragments of the same mineral Minerals (cont.) Minerals (cont.) • What does “naturally occurring” mean? • It means you will find these substances in nature – they are not made in a laboratory • They are formed by natural processes • “Solid” means that minerals can maintain their shape indefinitely • They will not conform to the shape of their container • Liquids like oil or water and gasses are therefore not regarded as minerals 2 Minerals (cont.) • What does “inorganic substance” mean? • It simply means that they do not contain organic chemicals • “organic chemical” means substances with carbon bonded to hydrogen along with varying amounts of oxygen, nitrogen ect. • Presence of carbon alone does not disqualify a substance from being a mineral (graphite, diamond and Calsium carbonate (CaCO3)are regarded as minerals Minerals (cont.) • “Characteristic atomic structure” means that atoms, ions, or molecules do not float about and rearrange into random configurations • They are fixed in a specific pattern that repeats at regular intervals • This orderly framework is called the crystal lattice Minerals (cont.) • “Definite chemical composition” means you can write a chemical formula for a mineral • Quartz has the formula of SiO2 • It therefore contains the elements silicon and oxygen in the proportion of one silicon atom for every two oxygen atoms Crystal lattice of Halite (NaCl) Snowflakes are symmetrical hexagons From: Marshack, S. 2001:Earth, Portrait of a Planet. WW Norton & Company, New York. Fig 5.7 Crystals have symmetry: one half is a mirror image of the other half (Diagrams from: Marshack, S. 2001:Earth,Portrait of a Planet. WW Norton & Company, New York. Fig 5.8) 3 Crystal shapes • Minerals therefore have shapes that identify them From: Marshack, S. 2001: Earth, Portrait of a Planet. WW Norton & Company, New York. Fig 5.5 4
