Lesson 2.1: Rocks PDF

LESSON 2.1: ROCKS ================= **Rock** - **naturally-occurring, coherent, aggregate of minerals** or solid materials such as natural glass or organic matter. - **found in the lithosphere** which is derived from the Greek word "*lithos"* meaning "stone" **Lithosphere** - rigi...

LESSON 2.1: ROCKS ================= **Rock** - **naturally-occurring, coherent, aggregate of minerals** or solid materials such as natural glass or organic matter. - **found in the lithosphere** which is derived from the Greek word "*lithos"* meaning "stone" **Lithosphere** - rigid, rocky outermost part of earth composed of the crust and uppermost part of the upper mantle. **Rock cycle** - model that describes all **the process by which rocks are formed, modified, transported, decomposed, melted, and reformed.** - occur **both on the earth\'s surface and underneath.** - dynamic cycle of processes and product. +-----------------------------------+-----------------------------------+ | **PROCESSES** | **PRODUCT** | +===================================+===================================+ | | Magma | +-----------------------------------+-----------------------------------+ | Crystallization | Igneous Rock | +-----------------------------------+-----------------------------------+ | Uplift and exposure | Sediments | +-----------------------------------+-----------------------------------+ | | Sedimentary Rocks | +-----------------------------------+-----------------------------------+ | | Metamorphic Rocks | +-----------------------------------+-----------------------------------+ 1. When **magma (molten rock beneath the surface) is exposed to lower temperature** minerals and amorphous solids crystallize, solidify and ***form igneous rock.*** 2. These rocks may then be brought to the surface through uplift where they are exposed to weathering and erosion the processes of weathering and erosion. 3. The processes of **weathering and erosion** break the rocks down into smaller pieces called ***sediments.*** 4. Sediments **undergo transportation** via agents such as wind, water, glaciers, rivers, and oceans until they settle in an area where they will **undertake deposition.** 5. As more material settle on top of each other, **temperature and pressure increase** and the sediments at the bottom **may undergo lithification.** 6. **Lithification transform sediments into *sedimentary rocks.*** 7. As temperature and pressure increase due to continuous burial and tectonic activity, the **sedimentary rocks undergo the process of metamorphism**, transforming them into ***metamorphic rocks.*** 8. If temperature continues to increase and exceeds the melting point of the rock, the **rocks will eventually undergo melting turning into *magma.*** 9. **Igneous rocks may be transformed into metamorphic rocks** without initially becoming a sedimentary rock. 10. **Metamorphic rocks may be weathered and eventually lithified into sedimentary rocks** without passing through process that produce igneous rocks. FORMATION OF IGNEOUS ROCKS -------------------------- **Igneous Rock** - formed from the cooling and solidification of magma or lava. - the word igneous is derived from the Latin *"igneus"* which means "fiery" or "on fire". - form at higher temperature than other types of rock. **3 ways in which igneous rocks can form:** +-----------------------+-----------------------+-----------------------+ | | | this results in the | | | | formation of crystals | | | | that are to the naked | | | | eye without the aid | | | | of a magnifying lens. | +=======================+=======================+=======================+ | | - 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. | | +-----------------------+-----------------------+-----------------------+ | **On the surface, | - this results in | | | from rapidly cooling | the formation of | | | lava** | very small | | | | crystals may not | | | | be visible | | | | without the use | | | | of a magnifying | | | | lens. | | | | | | | | - igneous rocks | | | | like these are | | | | called extrusive | | | | or volcanic, | | | | since they are | | | | usually extruded | | | | during volcanic | | | | eruptions. | | | | | | | | - examples of these | | | | rocks are basalt, | | | | andesite, and | | | | rhyolite. | | +-----------------------+-----------------------+-----------------------+ | **On the surface, | - when volcanoes | | | from the | erupt violently, | | | consolidation of | the lava exiting | | | particles erupted by | the volcanoes are | | | explosive volcanic | ripped apart into | | | activity** | smaller pieces by | | | | rapidly expanding | | | | gases in the | | | | lava, just like | | | | the bubbles in a | | | | bottle of soft | | | | drinks shaken | | | | vigorously. | | | | | | | | - depending on how | | | | much gas is | | | | present, the | | | | particles may | | | | solidify as small | | | | as ash or as | | | | large as | | | | basketballs. | | | | | | | | - when these | | | | particles come | | | | together on the | | | | surface via | | | | lithification, | | | | they form | | | | pyroclastic | | | | igneous rocks. | | | | | | | | **Pyroclastic Igneous | | | | Rocks** | | | | | | | | - a hybrid of | | | | igneous and | | | | sedimentary | | | | processes. | | | | | | | | - relevant in the | | | | Philippine | | | | setting because | | | | it is a common | | | | eruptive product. | | | | | | | | - Examples: | | | | ignimbrite | | | | (locally known as | | | | adobe), tuff, and | | | | volcanic breccia. | | +-----------------------+-----------------------+-----------------------+ FORMATION OF SEDIMENTARY ROCKS ------------------------------ **Sedimentary Rock** - products of the lithification of particles produced by weathering of other pre-existing rocks. - Can have parent material derived from older igneous, metamorphic, and even sedimentary rocks. - they may also be comprised of mineral fragments and organic material, or in some cases, minerals that precipitate from solution called sediments. - 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. - may form on the Earth's surface or may form underneath, but not in environments where they are subjected to igneous processes. - sedimentary lithification occurs at a lower temperature than that of igneous rocks. **3 ways in which sedimentary rocks can form:** +-----------------------+-----------------------+-----------------------+ | | | This process produces | | | | sedimentary rocks | | | | that are considered | | | | as clastic, which are | | | | differentiated based | | | | on the size of the | | | | sediments or clasts | | | | in the rocks. | | | | | | | | Examples of these | | | | rocks include shale, | | | | sandstone, and | | | | conglomerate. | +=======================+=======================+=======================+ | | | Rocks that are | | | | exposed to water and | | | | Oxygen can undergo | | | | chemical changes such | | | | as oxidation Rocks | | | | that are colysis | | | | through time | | | | sedimentary rocks. | +-----------------------+-----------------------+-----------------------+ | | | These processes break | | | | down rocks into their | | | | chemical components, | | | | hudularly 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, | | | | leading to the | | | | formation of | | | | *chemical sedimentary | | | | rocks.* | +-----------------------+-----------------------+-----------------------+ | | | Examples of these | | | | types of rocks | | | | include limestone, | | | | dolostone, and rock | | | | salt. | +-----------------------+-----------------------+-----------------------+ | | | - These types of | | | | sedimentary rocks | | | | are called | | | | bioclasts. | | | | | | | | - Examples of | | | | bioclastic | | | | sedimentary rocks | | | | are coquina and | | | | organic | | | | limestone. | +-----------------------+-----------------------+-----------------------+ FORMATION OF METAMORPHIC ROCKS ------------------------------ **Metamorphic Rock** - - - **The two major types of metamorphism depend on which factor causes the alteration of the parent rock:** usually due to tectonic activity, the flat and/or elongated mineral components of the preexisting rocks react by aligning perpendicular to the axis of the pressure. -- -- ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- this results in a 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. This type of metamorphism is called ***regional metamorphism***, since tectonic processes involved in this process, which produces mountain chains, are regional in scale. Examples of foliated rocks are **slate, schist, and gneiss.** 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. This process is called ***contact metamorphism.*** Contact metamorphism ***creates non foliated metamorphic rocks***, such as **marble and quartzite.** - LESSON 2.2: CLASSIFICATION OF ROCKS =================================== **Rocks** - **can be classified based on the differences in their texture and composition.** - These factors are controlled by the processes that formed the rock. - rock's texture could provide information about the environment where the rock was formed. - igneous, sedimentary, and metamorphic processes are distinct, their resulting textures are also distinct. **\*Texture refers to the size, shape, and arrangement of mineral grains and other constituents in a rock.** +-------------+-------------+-------------+-------------+-------------+ | | - - - | | | | | | | | | | +=============+=============+=============+=============+=============+ | | | | - from | | | | | | slowly- | | | | | | cooled | | | | | | magma | | | | | | have | | | | | | time to | | | | | | form | | | | | | large | | | | | | mineral | | | | | | crystal | | | | | | s | | | | | | that | | | | | | are | | | | | | visible | | | | | | without | | | | | | the aid | | | | | | of a | | | | | | magnify | | | | | | ing | | | | | | lens. | | | | | | | | | | | | - The | | | | | | resulti | | | | | | ng | | | | | | texture | | | | | | is | | | | | | called | | | | | | phaneri | | | | | | tic, | | | | | | which | | | | | | is | | | | | | derived | | | | | | from | | | | | | the | | | | | | Greek | | | | | | phanero | | | | | | s, | | | | | | meaning | | | | | | "visibl | | | | | | e." | | | | | | | | | | | | - In | | | | | | cases | | | | | | when | | | | | | mineral | | | | | | s | | | | | | crystal | | | | | | lize | | | | | | very | | | | | | slowly | | | | | | at | | | | | | depth, | | | | | | the | | | | | | resulti | | | | | | ng | | | | | | texture | | | | | | is | | | | | | pegmati | | | | | | tic, | | | | | | one | | | | | | that is | | | | | | compose | | | | | | d | | | | | | of very | | | | | | large | | | | | | crystal | | | | | | s | | | | | | (larger | | | | | | than 2 | | | | | | to 3 | | | | | | cm). | | +-------------+-------------+-------------+-------------+-------------+ +-------------+-------------+-------------+-------------+-------------+ | | | | - from | | | | | | rapidly | | | | | | -cooled | | | | | | magma | | | | | | usually | | | | | | exhibit | | | | | | aphanit | | | | | | ic | | | | | | texture | | | | | | s. | | | | | | | | | | | | - Aphanit | | | | | | ic | | | | | | is | | | | | | derived | | | | | | from | | | | | | the | | | | | | Greek | | | | | | apbaner | | | | | | os, | | | | | | which | | | | | | means | | | | | | "invisi | | | | | | ble." | | | | | | Thus, | | | | | | the | | | | | | mineral | | | | | | crystal | | | | | | s | | | | | | of | | | | | | aphanit | | | | | | ic | | | | | | rocks | | | | | | cannot | | | | | | be | | | | | | disting | | | | | | uished | | | | | | without | | | | | | the use | | | | | | of | | | | | | magnify | | | | | | ing | | | | | | tools. | | | | | | | | | | | | - A | | | | | | special | | | | | | volcani | | | | | | c | | | | | | texture | | | | | | is | | | | | | display | | | | | | ed | | | | | | by | | | | | | rocks | | | | | | that | | | | | | cool | | | | | | rapidly | | | | | | , | | | | | | as | | | | | | mineral | | | | | | crystal | | | | | | s | | | | | | do nor | | | | | | form, | | | | | | which | | | | | | usually | | | | | | occur | | | | | | when | | | | | | lava is | | | | | | expelle | | | | | | d | | | | | | underwa | | | | | | ter. | | | | | | This | | | | | | results | | | | | | in | | | | | | rocks | | | | | | that | | | | | | appear | | | | | | glassy. | | | | | | Another | | | | | | is the | | | | | | vesicul | | | | | | ar | | | | | | texture | | | | | | , | | | | | | which | | | | | | is a | | | | | | result | | | | | | of | | | | | | gases | | | | | | escapin | | | | | | g | | | | | | while | | | | | | the | | | | | | volcani | | | | | | c | | | | | | rock is | | | | | | being | | | | | | formed. | | +=============+=============+=============+=============+=============+ | | | the | | | | | | result of | | | | | | the | | | | | | lithificati | | | | | | on | | | | | | of erupted | | | | | | volcanic | | | | | | material; | | | | | | thus, these | | | | | | types of | | | | | | rocks are | | | | | | distinguish | | | | | | ed | | | | | | from one | | | | | | another by | | | | | | the size of | | | | | | their | | | | | | particle | | | | | | components. | | | +-------------+-------------+-------------+-------------+-------------+ | | - - - | | | | | | | | | | +-------------+-------------+-------------+-------------+-------------+ | | | | | | +-------------+-------------+-------------+-------------+-------------+ | | | | may also | | | | | | be | | | | | | described | | | | | | based on | | | | | | their sizes | | | | | | and are | | | | | | divided | | | | | | into three | | | | | | types: | | +-------------+-------------+-------------+-------------+-------------+ | **Metamorph | - may be | | | | | ic** | ***foli | | | | | | ated*** | | | | | **Rocks** | when | | | | | | the | | | | | | dominan | | | | | | t | | | | | | agent | | | | | | of | | | | | | metamor | | | | | | phism | | | | | | is | | | | | | pressur | | | | | | e, | | | | | | or | | | | | | ***crys | | | | | | talline*** | | | | | | when | | | | | | the | | | | | | dominan | | | | | | t | | | | | | agent | | | | | | is | | | | | | beat. | | | | | | | | | | | | - Mostly | | | | | | compose | | | | | | d | | | | | | of | | | | | | mineral | | | | | | s | | | | | | that | | | | | | only | | | | | | form at | | | | | | high | | | | | | tempera | | | | | | ture | | | | | | and | | | | | | pressur | | | | | | es | | | | | | associa | | | | | | ted | | | | | | with | | | | | | the | | | | | | process | | | | | | of | | | | | | metamor | | | | | | phism. | | | | | | These | | | | | | mineral | | | | | | s | | | | | | are | | | | | | known | | | | | | as | | | | | | ***inde | | | | | | x | | | | | | mineral | | | | | | s**.* | | | | | | | | | | | | 1.Plary or | | | | | | elongated | | | | | | minerals | | | | | | align | | | | | | themselves | | | | | | parallel to | | | | | | the axis of | | | | | | pressure, | | | | | | resulting | | | | | | in a | | | | | | layered | | | | | | appearance | | | | | | or | | | | | | foliation. | | | | | | Minerals | | | | | | differ in | | | | | | foliation | | | | | | based on | | | | | | their | | | | | | composition | | | | | | : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | the | | | | | | rock may no | | | | | | t appear fo | | | | | | liated to t | | | | | | he naked ey | | | | | | e. | | | | | | The foli | | | | | | ation, howe | | | | | | ver, will m | | | | | | anifest its | | | | | | elf physica | | | | | | lly in the | | | | | | rock's tend | | | | | | ency to sep | | | | | | arate along | | | | | | parallel p | | | | | | lanes.< | | | | | | /th> | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This ty | | | | | | pe of textu | | | | | | re is calle | | | | | | d slaty. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | their a | | | | | | lignment re | | | | | | sults in an | | | | | | obvious bu | | | | | | t not clear | | | | | | ly-defined | | | | | | foliation. | | | | | | This type o | | | | | | f texture i | | | | | | s called ph | | | | | | yllitic. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | their l | | | | | | ayering is | | | | | | more distin | | | | | | ct, resulti | | | | | | ng in a tex | | | | | | ture called | | | | | | schiste. T | | | | | | hese types | | | | | | of rocks ar | | | | | | e usually c | | | | | | omposed of | | | | | | platy miner | | | | | | als like ch | | | | | | lorite, gra | | | | | | phite, biot | | | | | | ite, and mu | | | | | | scovite. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | the roc | | | | | | k exhibits | | | | | | a coarsely- | | | | | | branded app | | | | | | earance due | | | | | | to the ali | | | | | | gnment of m | | | | | | inerals lik | | | | | | e amphibole | | | | | | , feldspar, | | | | | | and quartz | | | | | |. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This ty | | | | | | pe of textu | | | | | | re is calle | | | | | | d grantic | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | result | | | | | | when the pa | | | | | | rent rock i | | | | | | s exposed w | | | | | | ith enough | | | | | | heat that i | | | | | | t induces r | | | | | | ecrystalliz | | | | | | ation of th | | | | | | e existing | | | | | | minerals. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | usua | | | | | | lly compose | | | | | | d of only o | | | | | | ne type of | | | | | | mineral. | | | | | | For exam | | | | | | ple, when a | | | | | | limestone | | | | | | composed of | | | | | | calcite th | | | | | | at precipit | | | | | | ated out of | | | | | | solution c | | | | | | omes in con | | | | | | tact with a | | | | | | n intrusive | | | | | | magma body | | | | | | , it metamo | | | | | | rphoses int | | | | | | o marble. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | But whe | | | | | | n conglomer | | | | | | ate rocks c | | | | | | omposed of | | | | | | rock and mi | | | | | | neral fragm | | | | | | ents underg | | | | | | o contact m | | | | | | etamorphism | | | | | | , the small | | | | | | er componen | | | | | | ts may recr | | | | | | ystallize, | | | | | | producing a | | | | | | metaconglo | | | | | | merate-a ro | | | | | | ck that phy | | | | | | sically res | | | | | | embles the | | | | | | parent mate | | | | | | rial, but i | | | | | | s more dens | | | | | | e and shows | | | | | | evidence o | | | | | | f deformati | | | | | | on. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | **Index | | | | | | minerals** | | | | | | | | | | | | - They | | | | | | aid in | | | | | | the | | | | | | identif | | | | | | ication | | | | | | of | | | | | | metamor | | | | | | phic | | | | | | rocks, | | | | | | as well | | | | | | as the | | | | | | tempera | | | | | | ture | | | | | | and | | | | | | pressur | | | | | | e | | | | | | when it | | | | | | was | | | | | | formed. | | | | | | | | | | | | - Include | | | | | | s | | | | | | sillima | | | | | | nite, | | | | | | kyanite | | | | | | , | | | | | | staurol | | | | | | ite, | | | | | | andalus | | | | | | ite, | | | | | | and | | | | | | some | | | | | | garnet. | | | | +-------------+-------------+-------------+-------------+-------------+ - can be used as an indicator of the composition of a rock or mineral. - can be used to identify the composition of most igneous rocks. Light colors (white, light gray, tan, and pink indicate a felsic composition. - Felsic compositions are rich in silica (SiO₂). - Dark colors (black and brown indicate a mafic composition of ultramafic composition. - Mafic compositions are poor in silica but rich in iron and magnesium. Intermediate compositions have an intermediate color-gray or consisting of equal part of dark and light mineral. - Obsidian is a volcanic glass which erupts as a lava flow. - Most obsidian is felsic in composition but will typically have a very dark color. - Dunite has ultramafic composition but is greenish in color because it is composed almost entirely of green mineral, olivine. LESSON 2.3: MINERALS ==================== **Minerals** defined as a **naturally occurring, inorganic, solid with a definite chemical composition and an ordered internal structure.** **General characteristics of minerals:** +-----------------------+-----------------------+-----------------------+ | | | minerals **exist | | | | naturally** | | | | | | | | steel and synthetic | | | | diamonds are created | | | | artificially and | | | | therefore are not | | | | minerals | +=======================+=======================+=======================+ | | | 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 | | | | and organic compounds | | | | is not a mineral | +-----------------------+-----------------------+-----------------------+ | | | all liquids and gases | | | | even those that are | | | | naturally formed such | | | | as petroleum are not | | | | considered mineral | +-----------------------+-----------------------+-----------------------+ | | | **ice formed in the | | | | glaciers is | | | | considered a | | | | mineral** but water | | | | is not | +-----------------------+-----------------------+-----------------------+ | | | the chemical | | | | composition of | | | | minerals should | | | | express the exact | | | | chemical formula with | | | | the elements and | | | | compounds in specific | | | | ways | | | | | | | | the only exception is | | | | the atomic | | | | substitution which is | | | | a characteristic of a | | | | certain mineral | +-----------------------+-----------------------+-----------------------+ | | | the atoms in minerals | | | | are organized in a | | | | regular repetitive | | | | geometric pattern or | | | | crystal structure | | | | volcanic glass even | | | | if it is from | | | | naturally is not | | | | considered a 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 minerals | | | | or amber obsidian | | | | opal and pearl | +-----------------------+-----------------------+-----------------------+ COMPOSITION OF MINERALS ----------------------- composed primarily of **silicon-oxygen tetrahedrons** -- -- -------------------------------------------------------------------------------------------------------------------------------------------- the **major rock forming minerals** including **olivine and quartz** consists of **metal cations bonded to oxygen** an ions common oxide materials are **magnetite and hematite** consists of **metal cation bonded to sulfide** common or minerals along with oxides since **metals form a high proportion of the mineral** examples of sulfides are **galena and pyrite** consist of a **metal cation** bonded to the so42 an ionic group usually **precipitate out of water near the earth\'s surface** an example of sulfate is **gypsum** composed of a **halogen ion such as chlorine or fluorine** which forms highlight or **rock salt and fluorite** characterized by the **presence of carbonic ion** which bonds elements such as **calcium or magnesium** to form **calcite and dolomite** consists of a **single metal** such as **copper and gold.** **Crystal structure** - **dependent on the chemical composition of the mineral** - minerals that have similar chemical composition often share the same crystal structure and generally belong to the same crystal system - six crystal system used in grouping minerals based on structure**: triclinic, monoclinic, orthorhombic, tetragonal, hexagonal, and isometric structures** ### PHYSICAL PROPERTIES OF MINERALS +-----------------------------------+-----------------------------------+ | **Crystal form** | since minerals have a definite | | | chemical composition, **it forms | | | a definite structure which | | | crystallizes into a specific | | | crystal form.** | +===================================+===================================+ | **Habit** | - the **outward appearance of | | | the mineral's crystal form** | | | | | | - it can be described as | | | **granular, tabular, | | | dendritic, acicular, massive, | | | reniform, drusy, or | | | encrusting** | +-----------------------------------+-----------------------------------+ | **Cleavage and fracture** | - the manner **in which a | | | minerals breaks is dependent | | | on its molecular bonding and | | | structure.** | | | | | | - **Cleavage - The tendency of | | | a mineral to break along | | | planes of weakness.** | | | | | | - can be described both in the | | | number and directions of | | | cleavage planes and its | | | quality (excellent, good, | | | poor, or absent). | | | | | | - **Excellent Cleavage:** will | | | break into smooth, flat, | | | parallel surfaces | | | | | | - **Good Cleavage**: will | | | result in small, smooth, | | | steplike flat surfaces | | | | | | - Cleavage surfaces are | | | difficult to identify in | | | minerals with **poor | | | cleavage** | | | | | | - Minerals that **do not have | | | cleavage** will fracture | | | either in an **irregular | | | manner or as conchoidal | | | fracture (smooth, curved | | | surfaces)** | +-----------------------------------+-----------------------------------+ | **Luster** | - describes the **appearance of | | | light as it is reflected off | | | its surface.** | | | | | | - minerals 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.** | +-----------------------------------+-----------------------------------+ | **Color** | - most obvious mineral property | | | | | | - **not a reliable feature for | | | identifying minerals because | | | it can be altered by chemical | | | impurities within its | | | structure.** | | | | | | - Quartz is colorless but | | | slight 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** | - **color of a mineral in its | | | powdered form.** | | | | | | - can be obtained by rubbing | | | the mineral on an abrasive | | | ceramic tile called ***streak | | | plate.*** | +-----------------------------------+-----------------------------------+ | **Hardness** | - **measurement of the strength | | | of the chemical bonds in its | | | structure.** | | | | | | - can be measured by scratching | | | it with another mineral or a | | | reference material with known | | | hardness. | | | | | | **Mohs scale of hardness** | | | | | | - relative measure of hardness | | | using common materials and | | | standard minerals to | | | represent a specific hardness | | | value. | | | | | | +---------+---------+---------+ | | | | **INDEX | **SCALE | **COMMO | | | | | MINERAL | ** | N | | | | | ** | | OBJECTS | | | | | | | ** | | | | +=========+=========+=========+ | | | | Diamond | 10 | Steel | | | | | | | file | | | | | | | (6.5) | | | | +---------+---------+---------+ | | | | Corundu | 9 | | | | | | m | | | | | | +---------+---------+---------+ | | | | Topaz | 8 | | | | | +---------+---------+---------+ | | | | Quartz | 7 | | | | | +---------+---------+---------+ | | | | Orthocl | 6 | | | | | | ase | | | | | | +---------+---------+---------+ | | | | Apatite | 5 | Glass | | | | | | | (5.5) | | | | | | | | | | | | | | Wire | | | | | | | nail | | | | | | | (4.5) | | | | | | | | | | | | | | Copper | | | | | | | coin | | | | | | | (3.5) | | | | | | | Fingern | | | | | | | ail | | | | | | | (2.5) | | | | +---------+---------+---------+ | | | | Fluorit | 4 | | | | | | e | | | | | | +---------+---------+---------+ | | | | Calcite | 3 | | | | | +---------+---------+---------+ | | | | Gypsum | 2 | | | | | +---------+---------+---------+ | | | | Talc | 1 | | | | | +---------+---------+---------+ | +-----------------------------------+-----------------------------------+ | **Density** | - - - | | | | | | Other properties with the | | | corresponding minerals that | | | exhibit these properties are as | | | follows: | | | | | | - - - - | +-----------------------------------+-----------------------------------+ LESSON 2.4: ORES AND MINERALS ============================= **Ores** - Naturally-occurring materials that can be profitably mined. - Can be mineral or rock or metallic or nonmetallic. - Natural rock or sediments containing one or more valuable mineral. - It is a metalliferous mineral, or an aggregate of metalliferous mineral and gangue (associated rock of no economic value), that can be mined at a profit. **Mineral ores** 1. **Gold ore** -- a rock with gold in it 2. **Iron ore** -- a rock with iron in it 3. **Copper ore** -- a rock with copper in it **Deposit** Geologic term -- -- ------------------------------------------------------------------------------------------ Designates a natural occurrence of a useful mineral Economic term Denotes a mineral deposit of sufficient extent and concentration to invite exploitation. **Rock or mineral is considered an ore based on the following:** 1. Overall chemical composition 2. Percentage of extractable resource with respect to its total volume 3. Market value of the resource LOCATING ORES ------------- **Ore bodies** - unevenly distributed throughout the Earth\'s crust. - the primary reason why a country will never be self-sufficient in terms of natural resources and supplies. Even if a country can meet its own needs for a given natural material today, its local resources will run out, and that country may eventually require import. **Potential ore bodies** - located by recognizing that a geologic process or combination of processes can produce a localized enrichment of one or more minerals, and that these processes only happen in particular types of environments. +-----------------------+-----------------------+-----------------------+ | | | most common type of | | | | ore mineral | | | | deposition process | | | | | | | | Hydrothermal fluids | | | | form when groundwater | | | | or seawater is heated | | | | by magma or when hot, | | | | aqueous solutions are | | | | expelled from a | | | | cooling plutonic | | | | body. | +=======================+=======================+=======================+ | | | This produces veins | | | | that host metals like | | | | gold, silver, and | | | | copper. | +-----------------------+-----------------------+-----------------------+ | | | lead to the | | | | alteration and | | | | recrystallization of | | | | minerals and aids the | | | | formation and | | | | localization of | | | | economically-importan | | | | t | | | | materials like | | | | graphite, marble, and | | | | asbestos. | +-----------------------+-----------------------+-----------------------+ | | | create ore minerals | | | | which are | | | | concentrated due to | | | | their premature | | | | recrystallization and | | | | separation from | | | | magma. | +-----------------------+-----------------------+-----------------------+ | | | consider a basaltic | | | | magma sitting in a | | | | magma chamber. | | | | Chromite (an ore | | | | mineral of chromium) | | | | is sometimes the | | | | first to crystallize | | | | from basaltic magma. | | | | But because the | | | | chromite crystals are | | | | solid and therefore | | | | denser than the | | | | surrounding molten | | | | magma, the chromite | | | | tends to accumulate | | | | at the bottom of the | | | | magma chamber. | +-----------------------+-----------------------+-----------------------+ | | | a special type of | | | | magma that originates | | | | deep within the | | | | mantle and is the | | | | source of diamonds, | | | | which only | | | | crystallize at depths | | | | greater than 150 km. | +-----------------------+-----------------------+-----------------------+ | | | erupted very rapidly | | | | from depth onto the | | | | Earth\'s surface. | +-----------------------+-----------------------+-----------------------+ | | | their passage through | | | | the crust and | | | | eventual | | | | solidification leaves | | | | behind kimberlite | | | | pipes, which are | | | | highly prized as | | | | diamond ores. | +-----------------------+-----------------------+-----------------------+ | | | form evaporate | | | | deposits from the | | | | precipitation of | | | | saltwater minerals | | | | (halite, gypsum, | | | | limestone) and the | | | | evaporation of lake | | | | water (anhydrite). | +-----------------------+-----------------------+-----------------------+ | | | tends to take | | | | sediments along. if | | | | the wave action and | | | | strength is constant, | | | | it causes a selective | | | | sifting effect that | | | | removes sediments and | | | | leaves behind those | | | | that are heavier in | | | | what are called | | | | ***placer | | | | deposits***. | +-----------------------+-----------------------+-----------------------+ | | | heavy minerals, such | | | | as gold, platinum, | | | | zircon, and diamonds | | | | are concentrated in | | | | this manner. | +-----------------------+-----------------------+-----------------------+ | | | all rocks exposed | | | | to oxygen and water | | | | undergo this | +-----------------------+-----------------------+-----------------------+ | | | chemical changes in | | | | their mineral | | | | components that | | | | result in their | | | | alteration into other | | | | minerals and into the | | | | formation of residual | | | | ore deposits. | +-----------------------+-----------------------+-----------------------+ | | | these types of ores | | | | are common in | | | | tropical areas where | | | | the climate is | | | | conducive to their | | | | formation. | +-----------------------+-----------------------+-----------------------+ | | | many of the altered | | | | materials are | | | | economically | | | | important, such as | | | | laterite, which is an | | | | important ore of | | | | iron, nickel, and/or | | | | aluminum. | +-----------------------+-----------------------+-----------------------+ MINING ORES ----------- **Mining** - set of processes in which useful resources are withdrawn from a stock of any nonrenewable resource. - within the context of Earth resources, mining usually refers to the extraction of mineral resources. - Is of critical importance to industrialized societies because some materials cannot be grown-they can only be mined. - controversial industry because it is usually associated with the neglectful and irresponsible practices. Hence, it is given a negative public image. **Mining ores** - an intensive and sophisticated process that varies depending on the mineral and on whether they are excavated, stripped, or brought via tunnels and shafts. **Steps done during mining:** Looking for the ore body-a deposit that can yield a large amount of the required ore mineral -- -- ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Extracting a part of the ore to determine the resulting ore, its quality, and the amount of ore minerals (grade) Determining the ore\'s size, shape, and grade distribution throughout the deposit to apply appropriate mining methods, blast and dig pattern designs, safety precautions, and efficiency and processing methods Considering the social and environmental aspects and finding ways of mitigating any consequence of the mining operation, with the purpose of bringing the area back as close to its original state as possible Creating the appropriate mine and operational design, and proceeding with the construction once all the necessary permits are acquired from the government and local communities Separation of high-grade ores from the rest of the deposit Crushing and concentration of ores; waste materials (tailings) are released Closure of the depleted mine; the mine site is cleaned up and reclaimed or rehabilitated for other purposes The nature of a mineral or metal determines the type of mining operation needed and the amount of waste produced in the extraction. **3 possible extraction methods** +-----------------------------------+-----------------------------------+ | **Sand and gravel extraction** | - very little waste rock is | | | left behind after the milling | | | process, as these types of | | | deposits are not economically | | | viable unless the ore is of | | | high grade. | +===================================+===================================+ | **Extraction from buried ore | - huge quantities of rock often | | bodies** | need to be removed and | | | discarded so that a | | | relatively small amount of | | | ore can be recovered (e.g. a | | | typical copper grade of 2% | | | produces 20kg of pure copper | | | metal from a tone or ore, | | | leaving 980kg of waste rock) | +-----------------------------------+-----------------------------------+ | **Ore processing** | - ore minerals are produced | | | from ores through crushing, | | | separating, and purifying. | +-----------------------------------+-----------------------------------+