TOPIC 11 Minerals, Rocks and Mineral Resources **Rocks and minerals make up the Earth’s Surface.** Minerals = a naturally occurring, inorganic, crystalline solid having a definite chemical composition. ~ it is inorganic because it has not been made or composed of life forms. ~ it is crystalline because its atoms have a specific arrangement, this is called a crystalline structure. Rock = a naturally formed solid that is a part of Earth or any other celestial body.

Element Composition of the Earth’s Crust 99 percent of the Earth’s crust is composed of only 8 to 90 naturally occurring elements. The Earth’s most abundant (amount existing) element in the crust is oxygen (O) followed by silicon (Si). Refer to Reference Tables pg. 11. In the ESRT, they list the abundant elements by volume and by mass. Make sure you choose the right value when asked.

Mono-mineralic – made up of only 1 mineral. Ex: salt Poly-mineralic – made up of 2 or more minerals. Ex: Granite **There are over 2,000 minerals but only a few rock forming minerals.** Feldspar Augite Quartz Garnet Mica Magnetite Calcite Olivine Hornblende Pyrite Kaolin Talc

Mineral Crystal Structure The mineral structure (internal arrangement of atoms) is responsible for many of its chemical and physical properties. Ex: Graphite / Diamond have the same chemical composition but different properties, ie: hardness and shape. Most rock forming minerals are silicates (meaning they contain silicon (Si) and oxygen (O). Minerals form by recrystallization of atoms – the arrangement of the matter as it turns to a solid.

Mineral Identification There are 6 ways to identify a mineral: 1) Color – some minerals have distinctive colors. Some minerals tarnish – not true color 2) Streak – color of a mineral in its powdered form. Most minerals have a clear or white streak. 3) Luster – how a mineral reflects light. a) metallic – shines like polished metal b) non-metallic – does not shine like polished metal. A non-metallic luster can be glassy, pearly, dull, waxy or earthy.

4) Hardness – a mineral’s resistance to being scratched a) A harder mineral will scratch a softer mineral b) Mohs Scale of Hardness – a scale that ranges from 1- 10, 1 being the softest and 10 being the hardest. Fingernail – 2.5 Penny – 3.0 Glass – 5.5 Steel file – 6.5 5) Cleavage – a mineral’s ability to split along flat surfaces. This is due to the internal arrangement of atoms. Example: Halite (salt) – NaCl * This mineral breaks off into small cubes * Fracture – when a mineral breaks leaving an irregular/uneven surfaces

6) Specific gravity – density of a mineral compared to the density of water. The specific gravity of water is 1. Example: Mineral x has a specific gravity of 3. (This means it is 3x’s the density of water)