Rocks and Minerals PDF

Rocks and Minerals JohnAldrichG. Cortez,RN Rocks and Minerals Earth’s materials include rocks and minerals. They exhibit characteristics features and have economic value. Earth’s rock undergo transformation. Rocks and Minerals Mineral – a naturally occurring, inorganic, solid material that...

Rocks and Minerals JohnAldrichG. Cortez,RN Rocks and Minerals Earth’s materials include rocks and minerals. They exhibit characteristics features and have economic value. Earth’s rock undergo transformation. Rocks and Minerals Mineral – a naturally occurring, inorganic, solid material that has a fixed structure and a definite chemical composition. Mineralogy – the study of minerals and their properties. Rocks and Minerals There are several laboratory and field techniques used to distinguish minerals based on physical and chemical properties. Some minerals can be identified with the use of high-powered instruments while some can be assessed through their physical properties. Rocks and Minerals Rocks – consist of aggregates of minerals. Minerals – the building blocks of rocks. They are made up of one or a number of chemical elements with a definite / orderly chemical composition and crystal structure. Physical Properties of Minerals 1. Color Depends on the elements which constitute the crystal lattice – the arrangement of atoms, or groups of atoms, in a specific pattern and with high symmetry. The reflection of certain wavelengths of light by the crystal lattice results in the color perceived by the observer. Physical Properties of Minerals 2. Streak the color of the mineral in its powdered form. Physical Properties of Minerals Mineral gems come in different colors and streak. Physical Properties of Minerals 3. Luster The relative differences in the opacity and transparency of a mineral as light is reflected on its surface. This describes the 'sparkles' of the mineral surfaces. Physical Properties of Minerals Minerals maybe opaque, translucent or transparent. Physical Properties of Minerals 4. Specific Gravity The ratio of the weight of the mineral to the weight of the water with an equal volume. It can be determined by using a balance. Physical Properties of Minerals Mineral Specific Gravity Copper 8.9 Silver 10.5 Lead 11.3 Gold 19 Physical Properties of Minerals 5. Hardness The measure of the resistance of a surface to abrasions or scratches. Dependent on the chemical composition and the crystalline structure of a mineral. Physical Properties of Minerals Physical Properties of Minerals Scale Description Field Hardness 1 Can be rubbed off on a finger 2 Can be scratched with a fingernail Guide 3 Can be scratched with a coin 4 Can be scratched with difficulty with a knife 5 Can be scratched with a knife blade 6 Can be scratched with a piece of glass 7 Can be scratched with a piece of quartz 8 – 10 Mineral is too hard to be included in this scale Physical Properties of Minerals 6. Cleavage The tendency of the mineral to be split or broken along flat surfaces. It is described how a mineral breaks along weakness plain. The quantity of cleavage can be described in how clearly or easily the mineral breaks like perfect, good, distinct, poor or indistinct. Physical Properties of Minerals 6. Fracture the texture or shape of the mineral’s surface when the mineral breaks into forms other than flat surfaces. 7. Tenacity refers to the behavior of the mineral under deformation or stress such as cutting, crushing, bending, or hitting. Physical Properties of Minerals 8. Crystal Habit The growth crystal pattern of a mineral as single or aggregated. Over all shape of a mineral. Common shapes include needlelike (acicular), plantlike (dendritic), kidney – shaped (reniform), elongated in one direction (prismatic) and broad and flat (tabular). Physical Properties of Minerals Chemical Properties of Minerals 1. Solubility The ability of a substance to dissolve in a solvent at a specified temperature. For example, biotite, a mineral commonly found in igneous rocks, is soluble in both acid and base solutions. The dissolution releases the loosely-bound potassium ions in the mineral. Chemical Properties of Minerals 2. Melting Point The temperature at which solid turns into liquid. Minerals composed of atoms that are tightly bonded within the crystal structure have high melting points. For example, quartz melts above 1670°C. Common Rock – Forming Minerals 1. Quartz A chemical composition of SiO2. It is a glassy-looking hard substance with white streaks. Despite its hardness, with a Mohs hardness of 7, it is quite brittle. Common Rock – Forming Minerals Pure quartz is clear and transparent. Colored varieties of quartz are due to elemental impurities built into its lattice. The grains of quartz, in general, are irregular in shape. Common Rock – Forming Minerals 2. Feldspar Has a chemical composition of XAl(1−2)Si(3−2)O8, where X is K, Ca, or Na. It is quite hard with a Mohs hardness of 6. Common Rock – Forming Minerals It is a light-colored material, usually white, but they can have lighter shades of red or green. It has a glassy luster. In rocks, feldspar forms rectangular crystals that break along flat faces. Common Rock – Forming Minerals 3. Mica Any group of hydrous potassium aluminum silicate minerals. The most common examples are clear muscovite and black biotite. Mica is soft, with Mohs hardness ranging from 2 to 2.5. Common Rock – Forming Minerals It is easily identified by its perfect cleavage, reducing it to thin smooth flakes. Its shine is responsible for the flashes of light in rocks such as granite and slate. Common Rock – Forming Minerals 4. Pyroxene Have a general composition of XY(Al,Si)2O6 where X is Ca or Mg and Y is either Mg,Fe,Al. Augite is the most common of this group. It has a glassy luster with streaks of white, light green, or light brown. Common Rock – Forming Minerals It is generally black in color and has stubby prismatic crystals. Its key feature is its two cleavages at around 90°. Common Rock – Forming Minerals 5. Amphibole Has a dark color with a Mohs hardness ranging from 5 to 6. Hornblende is the most common amphibole. Common Rock – Forming Minerals It has a glassy luster and an opaque characteristic. Its crystals are very long and very thin. Common Rock – Forming Minerals 6. Olivine A silicate mineral with a general chemical composition of (Mg,Fe)2 SiO4, but calcium, manganese, and nickel can be substituted for magnesium and iron. It is known for its distinct olive-green color and commonly used in the gemstone industry as peridot. Common Rock – Forming Minerals It is a glassy looking and transparent substance that is almost as hard as quartz. Its crystals have a granular shape.  “I believe that even though you made this mistake, you will be okay. I believe we survive. I believe that believing we survive is what makes us survive.” -Dr. Izzie Stevens