Rock-Forming-Minerals.docx

ROCK-FORMING MINERALS - It is a naturally occurring substance; - It is an inorganic substance; - It has an orderly internal structure, and; - It has a fixed (or uniformly variable) chemical composition. 1. **Luster** 2. **Color**  3. *...

ROCK-FORMING MINERALS - It is a naturally occurring substance; - It is an inorganic substance; - It has an orderly internal structure, and; - It has a fixed (or uniformly variable) chemical composition. 1. **Luster** 2. **Color**  3. **Streak** 4. **Hardness**  5. **Cleavage**  6. **Fracture** 7. **Crystal Form**   a. Crystal faces are normally smooth, whereas cleavage planes, though also smooth, commonly are broken in a step-like fashion; b. Some crystal faces have fine grooves or ridges on their surfaces ***(Figures 9, 10)*** whereas cleavage planes do not. Similar looking, very thin, parallel grooves, or striations, are seen on plagioclase cleavage surfaces, but these features persist throughout the mineral and are not surficial, as described below; c. Finally, unless crystal faces happen to coincide with cleavage planes, the mineral will not break parallel to them. 8. **Specific Gravity** 1. **Solubility** refers 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. 2. **Melting point** refers to 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. 3. **Crystallographic techniques** such as X-ray diffraction are performed to determine the crystal structure of the mineral. COLOR -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- LUSTER -- -- -- -- -- -- -- -- -- -- -- -- C. **CRYSTAL FORMS** -- -- -- -- -- -- -- -- -- -- -- -- BACKGROUND INFORMATION FOR LEARNERS CLASSIFICATION OF ROCKS 1. **Sedimentary rocks-** These are the products of the lithification or particles produced by the weathering of other pre-existing rocks (older igneous, metamorphic or even sedimentary rocks), mineral fragments, organic materials or minerals that precipitate from solution. Collectively, these components are called *sediments.* The term is derived from the Latin *sedentarius*, which means "sitting", as these sediments will eventually be deposited and settle until they are transformed into sedimentary rocks. 1. **Clastic-** Sedimentary rocks are formed from the cementation of sediments or lithification of rock and mineral fragments that have been deposited, buried and compacted over a long period of time. Example of these rocks include shale, sandstone and conglomerate. 2. **Crystalline.** They are also formed from the precipitation of minerals from ions in solution. Rocks that are exposed to water and oxygen can undergo chemical changes such as oxidation and hydrolysis through time. These processes break down rocks into their chemical components, particularly into ions that can be carried by running water in solution. Once the solution is saturated, the precipitation of minerals like calcite and halite can occur**.** Examples of these types of rocks include limestone, dolostone and rock salt. 3. **Bioclasts.** Sedimentary rocks can also form from the compaction and cementation of plant and/or animal remains. Examples of these rocks are coquina and organic limestone.  Coal Dolomite Halite Hematite Limestone Sandstone 2. **Igneous rocks-** These are formed from the cooling and solidification of magma or lava. The word "igneous" is derived from Latin *igneus*, which means "fiery" or on "fire". Igneous rocks form at higher temperatures than other types of rocks. 1. *Below the surface,* from slowly cooling magma- This results in the formation of crystals that are visible to the naked eye without the aid of a magnifying lens. The resulting texture is called *phaneritic,* which is derived from the Greek *phaneros,* meaning "visible". These types of igneous rocks are called ***intrusive* or *plutonic***, since they cool underneath the surface as plutons. Examples of these rocks include granite, diorite, and syenite. 2. *On the surface,* from rapidly cooling lava- This results in the formation of very small crystals that may not be visible without the use of a magnifying lens. These types of igneous rocks are called ***extrusive* or *volcanic***, since they are usually extruded during volcanic eruptions. Examples of these are basalt, andesite, and rhyolite. 3. *On the surface*, from the consolidation of particle erupted by explosive volcanic activity-When volcanoes erupt violently, the lava exiting the volcanoes are ripped apart into smaller pieces by rapidly expanding gases in the lava, just like the bubble in a bottle of soft drinks shaken vigorously. Depending on how much gas is present, the particles come together on the surface via lithification, they form ***pyroclastic igneous rocks**. Pyroclastic* is derived from the Greek *pyro* which means "fire" and *klastos* which means "shattered". Examples of these type are ignimbrite (adobe), tuff and volcanic breccia. - *Felsic*: also called granitic; \>65% silica, generally light-colored intermediate: also called andesitic; 55-65% silica; generally medium colored (medium gray) - *Mafic*: also called basaltic; 45-55% silica; generally dark colored - *Ultramafic*: \ 1. ***Regional Metamorphism*-** When the dominant altering factor is pressure, usually due to tectonic activity, the flat and/or elongated mineral components of the pre-existing rocks react by aligning perpendicular to the axis of the pressure. This results in layered or banded appearance in the rocks called *foliation,* and these types of rocks are called *foliated metamorphic rocks.* The term comes from the Latin *folium* which means "leaf", where the flat leaves are on top of each other. Examples of these include slate, schist, and gneiss. 2. ***Contact Metamorphism***- When the dominant altering factor is heat, usually from direct contact between an older rock material and an intruding body of magma, the parent rocks may undergo a fundamental change in texture due to recrystallization, or even change in mineralogy when chemically-active fluids are also involved. It results in rocks like marble and quartzite that are called *non-foliated metamorphic rocks*. 3. ***Dynamic Metamorphism***- Happens due to instantaneous events such as faulting. 4. ***Shock Metamorphism**-* Happens due to meteorite impact. Examples of Metamorphic Rocks LEARNING COMPETENCY a. identify the different processes involved in the rock cycle; b. illustrate the rock cycle; c. identify the different rock types; d. explain how each type is formed; e. classify rocks into igneous, sedimentary and metamorphic; and f. explain the relevance of classifying rocks with civil engineering. ACTIVITY 1 GUIDE QUESTIONS 1. What are the three basic types of rocks? 2. Using the chart below, describe the types of rock through the crayon rock activity. -- -- -- -- ACTIVITY 2: MEETING THE ROCKS 1. What are the three (3) basic classification of rocks? 2. How do sedimentary rocks form? 3. How do igneous rock form? 4. How do metamorphic rocks form? 5. Complete the concept map below: