Earth Materials and Processes: Minerals and Rocks PDF

EARTH MATERIALS AND PROCESSES: MINERALS AND ROCKS Prepared by: Ms. Ma. Ruszeth S. Belandres, LPT, MEd – Natural Science Most Essential Classify rocks into Learning igneous, sedimentary, a...

EARTH MATERIALS AND PROCESSES: MINERALS AND ROCKS Prepared by: Ms. Ma. Ruszeth S. Belandres, LPT, MEd – Natural Science Most Essential Classify rocks into Learning igneous, sedimentary, and Competency metamorphic. Objectives: 1. Identify the three types of rocks. 2. Classify rocks as to igneous, sedimentary and metamorphic rocks. 3. Appreciate the importance of rocks in our daily life. INTRODUCTION Minerals and rocks are the significant building blocks of our dynamic Earth. They make up the solid part of the lithosphere and provide us with valuable resources. There are over 5,000 minerals but only a few occur as rock – forming minerals. Rocks are classified according to their origin of formation. Over time, rocks are gradually transformed from one type to another in what we call rock cycle. The origin of any particular rock is determined by careful examination of its texture, composition, and internal structure. This is the basis of rock identification and classification. The word “rock” refers to the solid mass of the lithosphere. A rock is a naturally occurring solid mixture of one or more different minerals and other organic matter. The science that is concerned with the study of rocks is called Petrology. The Three Main Categories of Rocks 1.Igneous Rocks 2.Sedimentary Rocks 3.Metamorphic Rocks Igneous Rocks Got its name from a Latin word “ignis” which means fire. The parent material is usually magma, a molten material from deep within the Earth that cools and hardens. This is an exothermic process (meaning heat is liberated) and involves a change of phase from the liquid to solid state. Generally, igneous rocks are hard and tough. This Photo by Unknown Author is licensed under CC BY Igneous Rocks: Varieties Texture (how big the crystals are) It relates to the general appearance of the rock The texture of the igneous rock is strongly affected by the rate of cooling of the magma that results in the formation of crystals (usually minerals). The slower the rate of the cooling, the larger the crystals found in the rock resulting in a course- grained igneous rock. On the other hand, the faster the rate cooling, the smaller the crystals are and resulting into a fine- grained igneous rock. Igneous Rocks: Varieties Composition (what they are made of) Refers to the elements in the magma that directly affect the kind of material that is formed when the magma cools. The composition of the igneous is directly related to where the magma is formed. Magmas associated with the crustal spreading are generally mafic while magmas associated with the crustal compression and subduction are termed felsic. Types of Igneous Rocks A. Igneous Intrusive or Plutonic Igneous Rocks B. Igneous Extrusive or Volcanic Igneous Rocks  A. Igneous Intrusive or Plutonic Igneous Rocks Some magmas rise and flow into the cracks in the crust but do not reach the surface; instead, they harden deep inside the crust. They cool slowly and take thousands or even millions of years to solidify. The cooling takes place very slowly because the surrounding rocks are also hot. When magmas solidify into igneous rocks, minerals are formed. The slow rate of cooling often forms large crystals visible enough to be seen even without the aid of a magnifying glass. Most common examples: 1. Granite – one of the most common type, light colored and coarse – grained rock. It is composed mainly of a mixture of several kinds of mineral, one of which is silicon dioxide (quartz), a clear colorless particle that resembles a broken glass. Granite can be sued a building stone, a material for monuments or statues. Nowadays, they are being used as counter tops in modern kitchens. 2. Gabbro – dark – colored igneous rock often called “black granite”. The dark color is due to a higher content of iron and magnesium but with a lower content of quartz. Formed by slow cooling, this process causes large crystals to form giving the rock a course – grained texture. 3. Diorite and andesite are also common igneous rocks in the Philippines.  B. Igneous Extrusive or Volcanic Igneous Rocks Sometimes magma may reach the surface or erupt onto the surface from volcanoes. This extrusion onto the surface is called lava. Lava cools faster and solidifies quickly when exposed to the atmosphere or into the water. The rapid cooling gives very little opportunity for large crystals to be formed. Due to the formation of small crystals, this gives igneous extrusive a fine – grained texture. Others would have no crystals at all, so they are described as glassy. Most common examples: Basalt – as a mafic silicate rock, usually dark – colored, hard, fine – grained and with high specific gravity (due to high content of iron and magnesium and some feldspar as well). Obsidian – formed from lava, also dark – colored but glassy. During early times, these rocks were used for weapon and tools by shaping them into pointed and sharped – edge objects. Pumice – characterized by the presence of many air holes, this is because gas bubbles are trapped in the rock during the colling process leaving tiny bubbles.it so light – colored with low density that it floats in water. Pumice is valuable for grinding, scrubbing, and polishing. Scoria – formed in the same manner as pumice, but it has larger holes and is much denser and darker. Sedimentary Rocks When igneous rocks are exposed at the surface, they begin to wear away. They are altered either by physical or chemical weathering processes. Heat from the sun breaks the rock apart. Rainwater may fill the cracks in the rocks and eventually break them down. Sedimentary rocks are formed from “lithification”, a process of cementing soft, unconsolidated sediments into hard rocks. Three Main Types of Sedimentary Rocks 1. Clastic sedimentary rocks are derived from mechanical weathering which involves the breakdown of rocks into smaller ones at the surface of the crust, accumulate as clasts, piled on top of one another and “lithified”. 2. Chemical sedimentary rocks form when dissolved materials precipitate. 3. Organic sedimentary rocks are formed by the accumulated sedimentary debris caused by organic processes. Common examples of Sedimentary Rocks 1. Conglomerate is a rock made up of pebbles, pieces of gravel cemented together. They are usually formed along beaches and at the foot of mountains, also in riverbeds. Conglomerate results into hills and ridges. 2. Sandstones are made of sand grains. This type of rock is composed mainly of mineral quartz. They are of medium weight and appear shiny and generally rough. Sandstones are strong and resistant to weathering. These rocks can be cut into blocks that can be used to build strong, beautiful walls, steps, or fences. Common examples of Sedimentary Rocks 3. Shale is a sedimentary rock made from layers of mud and chemical mixed with fine sand, organic matter, iron oxide and other impurities. It is the most common sedimentary rock. It appears smooth and is a soft rock that easily breaks into layers. It is either brown or gray in color. 4. Limestone is made up of mostly calcium carbonate. This rock came from dead organisms. As these organisms died, their bodies were trapped in stratified sediments and through time and great pressure, are cemented together. They are gray in color and is heavy. Metamorphic Rocks In geology, nothing is forever, everything changes. The metamorphic rocks get their name from “meta” (change) and “morph” (form). Earth movements can cause rocks to be pressed, bent or deeply buried under layers of other rocks. This can lead to an increase in pressure and temperature. Types of Metamorphic Rocks A. Non – foliated metamorphic rocks Marble Quartzite B. Foliated metamorphic rocks Slate Serpentine Gneiss A. Non – foliated metamorphic rocks These rocks are formed around igneous intrusive. When the rocks are heated by the intrusion, it results in the recrystallization of the minerals within the rock. Non – foliated metamorphic rocks show colored bands that reflect very small impurities. They have uniform texture and do not have a parallel layered appearance. They are better identified based on their composition. Examples of non – foliated metamorphic rocks 1. Marble is derived from limestone (its parent rock). It is a hard crystalline rock and is considered as the most beautiful rock because of it shimmering luster. It is used to make buildings, sculptures, monuments, household floorings, and kitchen counter tops. 2. Quartzite is derived from sandstone. It is very hard and durable. Quartzite can be ground down and used in glass making and in the manufacture of sandpaper. It is not always white, some are reddish due to iron oxide. B. Foliated Metamorphic Rocks These are metamorphic rocks formed within the earth’s interior under extremely high temperature and unequal pressure. This case of different pressures causes the minerals in the original rock to reorient themselves. The long ang flat minerals align themselves perpendicular to where the greatest pressure is directed. This tends to reduce the overall pressure on the rock giving the rock a layered band appearance. Foliated rocks are better identified on the basis of their texture. Examples of Foliated Metamorphic Rocks 1. Slate is derived from shale. It is a fine- grained rock. It is frequently gray in color and mainly made of the mineral quartz and muscovite along with hematite, biotite, and pyrite. The word “slate” is also used for certain types of objects made from slate rock. It is used extensively as roof tile or writing slate and blackboard. 2. Serpentine is used for both mineral and a metamorphic rock. It originates from basalt. It varies from light green to a dark green color with veins and fractures. Usually soft for table tops and flooring. 3. Gneiss is derived from conglomerate. It often contains feldspar or quartz. Its grain texture is coarse, making the layered bands of alternating minerals highly visible. Types of Metamorphism 1. Contact (thermal) Metamorphism evolves when rocks near igneous intrusive get heated. This produces non – foliated metamorphic rocks. 2. Regional (pressure) Metamorphism affects a larger area, commonly due to mountain formation. Foliated rocks are produced, and strong pressure effects are greatly seen on them. Investigating Minerals That Make Up Rocks Most Essential Identify common rock- Learning forming minerals using their physical and Competency chemical properties. Objectives: 1. Identify the examples of minerals. 2. Explain the different characteristics of minerals. 3. Differentiate minerals based on their properties 4. Develop awareness on the importance of minerals around us. Introduction Rocks are mixtures of different minerals. Some rocks are made up of many minerals while others are made of just one mineral. The minerals that make up rocks are called rock – forming minerals. Only a few minerals are rock – forming. Minerals are naturally occurring homogenous inorganic solid substance (either element or compound) having a definite chemical composition and characteristic crystalline structure or shape, color and hardness. Minerals of the same kind have the same crystal shape. Physical Properties of Minerals: Color Minerals have different colors depending on how they are formed. It is the most obvious property but not always definitive. The color of gold helps people identify it. Sulfur is always yellow, its fixed color and yet there are a few others of the same color. Most minerals are not always of the same color, but just a small amount of impurity can drastically alter a mineral’s color.  Luster is the way light interacts Physical with the surface of a crystal or mineral. The word traces back to Properties of the Latin word “lux” which means light and generally Minerals: Luster implies radiance, gloss, brilliance, or sparkle. Minerals have their own way of reflecting light. Mostly metallic minerals have luster. Copper for example, is shiny. But opal, although non – metallic has pearly luster. There are some minerals that are not shiny, like chalk Physical Properties of Minerals: Streak Streak refers to the color displayed in finely powdered form left behind when rubbed on a rough surface. The streak may be different from the color of the mineral itself. One of the simplest way ways of determining the streak of a mineral is through a “streak test” performed by rubbing or scraping the mineral across a piece of unglazed porcelain known as streak plate. Best examples are hematite which always produces a red brown streak and chromite which can be distinguished by its chocolate – brown streak. Pyrite and gold are of the same color and yet pyrite leaves a greenish – black streak while gold always leave a gold streak. Physical Properties of Minerals: Hardness This refers to the resistance of a mineral to scratching, it does not refer to how easily the mineral is broken. Hardness is a measure of the bonding strength between atoms. If these bonds are strong, the mineral is not easily scratched. Harder substances can scratch softer ones but not the other way around. Physical Properties of Minerals: Specific Gravity The specific gravity of a mineral refers to the mass of the mineral compared to the mass of an equal volume of water. Specific gravity is numerically equal to the density of a mineral in g/cm3. this is a useful way to identify a pure mineral. This was the method used by Archimedes when he tested the purity of the gold crown of his king. Physical Properties of Minerals: Cleavage or Fracture Cleavage is how smoothly the minerals break. If the minerals break apart in similar pieces, it is said to have good cleavage. And if it breaks like a piece of glass with uneven, jagged edges, it is classified as fracture. Mica is an example with perfect cleavage in one direction that is easy to produce. On the other hand, Quartz shows a good example of a fracture. If it splits, it would be broken in different shapes and sizes. End of Presentation