Publicité
Publicité

Contenu connexe

Publicité

Q1C2L1 Rocks and Minerals.pptx

  1. Lesson 1: Minerals Lesson 2: Rocks and Rock Cycle Lesson 3: Classification of Rocks Lesson 4: Ores and Minerals Chapter 2: Rocks and Minerals
  2. Lesson 1: Minerals • Earth is one of the four terrestrial planets in the solar system. The geosphere, which is one of the four interacting spheres that allow life to exist, refers to the solid Earth. It is composed of rock and regolith which are essentially aggregates of various minerals.
  3. Mineral •Is defined as a naturally occurring, inorganic solid with a definite chemical composition and an ordered internal structure. Every mineral is unique, but they exhibit general characteristics.
  4. Characteristics of minerals •Naturally occurring •Inorganic •Solid •Definite chemical composition •Ordered internal structure
  5. Naturally occurring •Minerals exist naturally. Steel and synthetic diamonds are created artificially, and therefore not minerals.
  6. Inorganic •Minerals are limited to substances formed through inorganic processes, and exclude materials derived from living organisms which involved organic processes. Coal, which is composed of remains of plants and other inorganic compounds, is not mineral.
  7. Solid •All liquids and gases-even those that are naturally formed such as petroleum- are not considered minerals. Ice formed in the glaciers is considered a mineral, but water is not.
  8. Definite chemical composition •The chemical composition of minerals should express the exact chemical formula with the elements and compounds in specific ratios. The only exception is the atomic substitution, which is characteristic of certain minerals.
  9. Ordered internal structure • The atoms in minerals are organized in a regular, repetitive geometric patterns or crystal structure. Volcanic glass, even if it is formed naturally, is not considered mineral because it is amorphous and has no form. Substances that fulfill all the requirements but do not have an ordered internal structure are called mineraloids. Examples of mineraloids are amber, obsidian, opal and pearl.
  10. Composition of minerals •In terms of composition, minerals can be classified into several classes which are mainly composed of elements that are abundant on Earth’s crust.
  11. 1. Silicates • Are composed primarily of silicon-oxygen tetrahedrons (Si𝑂4 2− ). Silicates are the major rock-forming minerals, including olivine ((𝑀𝑔, 𝐹𝑒)2 Si𝑂4) and quartz (Si 𝑂2).
  12. 2. Oxides •Consist of metal cations bonded to oxygen anions. Common oxide minerals are magnetite (𝐹𝑒3 𝑂4) and Hematite (𝐹𝑒2
  13. 3. Sulfides •Consist of metal cation bonded to sulfide (𝑆2− ). They are common ore minerals along with oxides since metals form a high proportion of the mineral. Examples of sulfides are galena (PbS) and Pyrite (Fe 𝑆2)
  14. 4. Sulfates •Consist of a metal cation bonded to the S𝑂4 2− anionic group. They usually precipitate out of water near Earth’s surface. An example of sulfate is gypsum (Ca𝑆𝑂4•2 𝐻2O)
  15. 5. Halides •Are composed of a halogen ion, such as chlorine or fluorine, which forms halite or rock salt (NaCl) and fluorite (Ca 𝐹2)
  16. 6. Carbonates • Are characterized by the presence of carbonic ion (C𝑂3 2− )which bonds elements such as calcium or magnesium to form calcite (Ca 𝐶𝑂3)or dolomite (CaMg(C𝑂3)2).
  17. Consists of single metal such as copper (Cu) and gold (Au). 7. Native metals
  18. Crystal structure of minerals • Is dependent on the chemical composition of the mineral. Minerals that have similar chemical compositions often share crystal structure and generally belong to the same crystal system. There are six crystal systems used in grouping minerals based on structure: triclinic, monoclinic, orthorhombic, tetragonal, hexagonal and isomeric structures.
  19. Physical properties of minerals • There are around 4,000 minerals, each with a unique set of physical properties, such as crystal formation, habit, cleavage, fracture, luster, color, streak, hardness, density, magnetism, taste, feel, and reaction to acid. These physical properties are useful for identifying minerals using a systematic method such as Dana Classification.
  20. Crystal form and habit • Since minerals have definite chemical composition, it forms definite structure which crystallizes into a specific crystal form. The outward appearance of the mineral’s crystal form, on the other hand, is its habit. It can be described as granular, tabular, dendritic, acicular, massive, reniform, drusy, or encrusting.
  21. Cleavage and fracture • The manner in which a mineral breaks is dependent on its molecular bonding and structure. The tendency of the mineral to break along planes of weakness is known as cleavage. It can be described both in the number and directions of cleavage plans and its quality (excellent, good, poor, or absent). Minerals with excellent cleavage will break into smooth, flat parallel surface. A good cleavage will result in small, smooth, step-like flat, parallel surfaces. Cleavage surfaces are difficult to identify in minerals with poor cleavage, while minerals that do not have cleavage will fracture either in an irregular manner or as conchoidal fracture (smooth, curved surfaces).
  22. Luster • The luster of the mineral describes the appearance of light as it is reflected off its surface. A mineral may be described as metallic, like that of a polished metal. Alternatively, it may be described as nonmetallic, which can be vitreous(like glass), resinous (like resin), pearlescent, silky, greasy, earthy, and dull.
  23. Color and streak • Although color is the most obvious mineral property, it is not a reliable feature for identifying minerals because it can be altered by chemical impurities within its structure. Quartz is colorless but slightly impurities can produce a variety of colors, such as white (like in milky quartz), yellow (like in citrine), purple (like in amethyst), or black (like in smoky quartz). • Streak is the color of a mineral in its powdered form. It can be obtained by rubbing the mineral on an abrasive ceramic tile called streak plate.
  24. Hardness • The hardness of a mineral is a measurement of the strength of the chemical bonds in its structure. It can be measured by scratching it with another mineral or a reference material with known hardness. The Mohs scale of hardness is a relative measure of hardness using common materials and standard minerals to represent a specific hardness value.
  25. Density •specific gravity is a measure of the density of a mineral. It is the weight of a mineral relative to the weight of an equal volume of water. Most common minerals have a specific gravity of 2.7, while gold has 19.
  26. Other properties with corresponding minerals that exhibit these properties are as follows: Magnetis m Taste Effervesce nce or reaction to acid Feel
Publicité