minerals

• Minerals, as building blocks of the earth, make up rocks
• Minerals have an orderly internal arrangement reflecting their internal structure and are crystalline solids
• Chapter 2: Minerals


  1. Physical and Chemical Properties of Minerals

  2. Classification of Minerals

  3. Rock-forming Minerals

  4. Variations in Chemical Composition of Minerals

  5. Stability Field of Minerals

  6. Summary

  7. Review Questions and Critical Thinking
• Understanding the different properties of minerals

  Important for mineral identification and classification
• Hardness is expressed according to the Moh’s Scale of Hardness ranked from 1 (softest) to 10 (hardest)
• Non-metallic minerals


  • serpentine
  • diamond
  • quartz
  • sphalerite
• Luster


  • Appearance of the surface of a mineral in reflected light, describing minerals as metallic or non-metallic
• Some solid substances without an orderly internal arrangement are classified as amorphous, examples of which are volcanic glass and opal
• Moh’s Scale of Hardness was designed by Friedrich Mohs, a German geologist and mineralogist, in 1812
• At the end of this chapter, students are expected to know the nature, the chemical and physical properties, and economic importance of minerals
• Hardness


  • Property referring to the mineral's resistance to scratching by another substance, measured by the mineral's ability to scratch another mineral
• Mineral


  Naturally occurring, inorganically formed, homogeneous solid with an ordered internal structure composed of atoms and ions, having a definite chemical composition and physical properties that vary within a certain range
• Metallic minerals

  • galena
  • gold
  • platinum
• Diamond is the hardest mineral due to its strong framework arrangement of atoms
• Minerals can be expressed as a chemical formula like quartz (silicon + oxygen → SiO2)
• Specimens of minerals belonging to the same species have the same internal geometric arrangement of atoms
• Students are expected to appreciate the significance of minerals to various geological processes and know the environment where minerals are formed and their importance to society
• Color is a property that is readily r
• Color is unreliable for identification in minerals that vary in colors due to impurities or tarnishing
• Color and Streak

  1. Color is the result of the reflection of light with the spectrum that the eyes can identify

  2. Streak is the color of the powdered form of a mineral
• Crystal Form


  • The external expression of the internal arrangement of atoms and molecules in a mineral
• Hardness scale

  • Fingernails (2-2.5), copper coin or wire (3-3.5), nail (5-5.5), glass (5.5), steel knife (6.5-7), porcelain (6.5), steel file (6-7)
• Mineral Structure


  • The regular arrangement of atoms that make up minerals is called their crystalline structure
• Graphite has weaker bonding between carbon atoms, making it one of the softest minerals
• Limonite is dark brown but has a yellow streak
• Hematite is red to black but has a red streak
• Minerals may have different colors from their streaks
• Diamonds have a strong covalent bonding structure, making them the hardest mineral
• Crystal faces vary in sizes but the angle between faces remains constant as governed by the Law of Constancy of Interfacial Angles
• Some minerals can exhibit a wide range of colors due to chemical impurities
• Crystal forms

  • Prismatic, tabular, bladed, platy, reniform, needle-like, cubic or equant
• In pyrite, the distance between Fe atoms is the same in all directions, unlike in marcasite
• Cleavage is the natural te
• Streak is more diagnostic than color in identifying minerals
• Minerals with unique identifying colors


  • Magnetite (Fe3O4) (black), galena (PbS) (gray), azurite (Cu3(CO3)(OH)2) (blue), malachite (Cu2(CO3)(OH)2) (green), sulfur (S) (yellow)
• Pyrite and marcasite have the same chemical composition (FeS2) but different crystalline structures
• Diamond and Graphite have the same chemical composition (carbon) but different crystalline structures
• Pyrite is yellow in color but has a black streak
• There are seven crystallographic systems among minerals—cubic, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, and triclinic
• Crystal form defines the relative growth of the crystal in three dimensions along the length, width, and height