[G11 STEM] Earth Science Lesson 2: Rocks and Minerals

Geosphere

Refers to the solid Earth. It is composed of rock and regolith which are essentially aggregates of various minerals.

Mineral

Is defined as a naturally occurring, inorganic solid with a definite chemical composition and an ordered internal structure.

Naturally-occurring

[General characteristics of minerals]

Minerals should exist naturally. Steel and synthetic diamonds are created artificially, and therefore, are not minerals.

Inorganic

[General characteristics of 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 inorganic compounds, is not a mineral.

Solid

[General characteristics of minerals]

All liquids and gases - even those that are naturally formed such as petroleum - are not considered minerals. Ice formed in the glaciers is considered a mineral but water is not.

Definite chemical composition

[General characteristics of minerals]

The chemical composition of minerals should express the exact chemical formula with the elements and compounds in specific ratios. The only exception is the atomic substitution, which is characteristic of certain materials.

Ordered internal structure

[General characteristics of minerals]

The atoms in minerals are organized in a regular, repetitive geometric patterns or crystal structure. Volcanic glass, even if it is formed naturally, is not considered a mineral because it is amorphous and has no form.

Mineraloids

are substance that fulfill all the requirements but do not have an ordered internal structure. Examples of this are amber, obsidian, opal, and pearl.

Silicates

are composed primarily of silicon-oxygen tetrahedrons; are the major rock-forming minerals and includes olivine and quartz.

Oxides

consist of metal cation bonded to oxygen anions. Common minerals are magnetite and hematite.

Sulfides

consist of metal cation bonded to sulfide. They are common ore minerals along with oxides since metals form a high proportion of the mineral. Examples of this are galena and pyrite.

Sulfates

consists of a metal cation bonded to the SO4^2- anionic group. They usually precipitate out of water near Earth's surface. An example is gypsum.

Halides

are composed of a halogen ion such as chlorine or fluorine which forms halite or rock salt and fluorite.

Carbonates

are characterized by the presence of carbonic ion which bonds elements such as calcium or magnesium to form calcite or dolomite.

Native metals

consist of a single metal such as copper and gold

Crystal structure

is dependent on the chemical composition of the mineral.

4000

There are around ___ minerals and each has a unique set of physical properties.

Dana classification

a systematic method used for identifying minerals

Habit

is the outward appearance of the mineral's crystal form. It can be described as granular, tabular, dendritic, acicular, massive, reniform, drusy, or encrusting.

Cleavage

is the tendency of a mineral to break along planes of weakness

Luster

describes the appearance of light reflected from a mineral surface

Color

is the most obvious mineral property, it is not a reliable feature for identifying minerals because it can be altered by chemical impurities within its structure.

Streak

is the color of a mineral in its powdered form. It can be obtained by rubbing the mineral on an abrasive ceramic tile called streak plate.

Hardness

The ___ of a mineral is a measurement of the strength of the chemical bonds in its structure.

Hardness

It can be measured by scratching it with another mineral or a reference material with known hardness.

Mohs scale of hardness

is a relative measure of hardness using common materials and standard minerals to represent a specific hardness value.

Specific gravity

is a measure of the density of a mineral. It is the weight of a mineral relative to the weight of an equal volume of water.

2.7

Most common minerals have a specific gravity of ___

19

Specific gravity of gold (Au)

Rock

is a naturally-occurring, coherent aggregate of minerals such as natural glass or organic matter.

Rocks

are found in the lithosphere which is derived from the Greek word 'lithos'

lithos

Greek word for 'stone'

Lithosphere

is the rigid, rocky, outermost part of Earth, composed of the crust and uppermost part of the upper mantle.

Rock cycle

is a model that describes all the processes by which rocks are formed, modified, transported, decomposed, melted, and reformed. These processes occur both on Earth's surface and underneath. Essentially, it is a dynamic cycle of processes and products.

uplift

the rising of regions of the Earth's crust to higher elevations

Lithification

the physical and chemical processes that transform sediments into sedimentary rocks

Metamorphism

the process in which one type of rock changes into metamorphic rock because of chemical processes or changes in temperature and pressure

Igneous rocks

are formed from the cooling and solidification of magma or lava. form at much higher temperatures compared to other types of rocks.

igneous

dervied from Latin 'igneus'

igneus

Latin word for 'igneous' which means 'fiery' or 'on fire'

Intrusive igneous rocks

also called plutonic igneous rocks

Intrusive igneous rocks

Igneous rocks that form below the surface, from slowly cooling magma; they cool underneath the surface as plutons.

Extrusive igneous rocks

Also called volcanic igneous rocks. Igneous rocks that form on the surface, from rapidly cooling lava; they are usually extruded during volcanic eruptions.

Pyroclastic rocks

rocks composed of fragments ejected during a volcanic eruption

Sedimentary rocks

are the products of the lithification of particles produced by the weathering of other pre-existing rocks.

Sediments

mineral fragments and organic material, or in some cases, minerals that precipitate from solution.

Sediments

The term was derived from the Latin sedentarius

Sedentarius

Latin word for sediments which means 'sitting'

Clastic

Sedimentary rock that forms from the cementation of sediments that have been deposited, buried, and compacted over a long period of time.

Chemical sedimentary rocks

rocks formed from minerals precipitated from a solution or left behind by evaporation

Bioclastic sedimentary rocks

Sedimentary rocks that form from the compaction and cementation of plant and/or animal remains.

Metamorphic rocks

form when preexisting or parent rocks are altered by heat, pressure, and the chemical activity of fluids.

Metamorphism

meaning "change in form". it usually occurs underneath the surface, although not as deep as the igneous environment.

Foliated metamorphic rocks

Layered or banded appearance in metamorphic rocks

Folium

Latin word for Foliated metamorphic rocks which means "leaf" where the flat leaves are on top of each other.

Regional metamorphism

as tectonic processes involved in this process are regional in scale that produces mountain chains. Examples of these include slate, schist, and gneiss.

Contact metamorphism

A change in the texture, structure, or chemical composition of a rock due to contact with magma.

nonfoliated metamorphic rock

metamorphic rock that does not exhibit a banded or layered appearance

Dynamic metamorphism

metamorphism that occurs as a consequence of shearing alone, with no change in temperature or pressure

Shock metamorphism

Metamorphism that occurs when minerals are subjected to high pressures and temperatures by heat and shock waves generated when a meteorite collides with Earth

Texture

refers to the size, shape, and arrangement of mineral grains and other constituents in a rock

Texture

A rock's _x_ could provide information about the environment where the rock was formed.

Phaneritic

coarse-grained, crystals are large enough to be seen w/out a microscope, formed by slow cooling (intrusive)

Phaneros

Greek word for Phaneritic, which means "visible"

Pegmatitic texture

a texture of igneous rocks in which the rocks are composed of very large crystals (larger than 2 to 3 cm)

Aphanitic

is derived from the Greek aphaneros which means "visible"

Aphaneros

Aphanitic is derived from the Greek _x_ which means "visible"

Aphanitic texture

A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished without the aid of a microscope.

Vesicular texture

Rock that has a spongy appearance due to trapped gas bubbles in the lava.

Porphyritic texture

An igneous rock texture in which large crystals are scattered on a background of much smaller crystals.

Pyroclastic

is derived from the Greek pyro which means "fire" and klastos which means "shattered."

Pyroclastic

This texture is the result of the lithification of erupted volcanic material; thus, these types of rocks are distinguished from each other by size of its particle components.

Igneous rocks

It is composed of felsic materials and mafic minerals.

Color

can be used as an indicator of the composition of a rock or mineral

Color index

can be used to identify the composition of most igneous rocks.

Felsic composition

light-colored igneous rocks

Felsic composition

igneous rocks that are rich in silica

Mafic composition

dark-colored igneous rocks

Mafic composition

igneous rocks that are poor in silica but rich in iron and magnesium

Intermediate compositions

igneous rocks that have an intermediate color - gray or consisting of equal parts of dark and light mineral.

Obsidian

is a volcanic glass which erupts as a lava flow.

Felsic

Most obsidian is _x_ 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

Clastic

Sedimentary rocks are _x_ when they form from lithification of rock and mineral fragments such as quarts, feldspar, and clay.

Crystalline

Sedimentary rocks are _x_ when they precipitate out of solution which forms dolomite, calcite, halite, or gypsum.

Bioclastic

Sedimentary rocks can be _x_ when it forms as the result of the accumulation of organic material or biologic activity. It may even contain remnants of plants, corals, shell, or fossil fragments.

Sedimentary clastic texture

may further be refined whether the shapes of the individual grains are angular or rounded.

Foliated

Metamorphic rocks may be _x_ when the dominant agent of metamorphic is pressure

Crystalline

Metamorphic rocks may be _x_ when the dominant agent of metamorphic is heat.

Foliation

Platy or elongated minerals align themselves parallel to the axis of pressure, resulting in a layered appearance or _x_

Slaty

If the minerals are microscopic, the rock may not appear foliated to the naked eye. The foliation however, will manifest itself physically in the rock's tendency to separate along parallel planes. This type of texture is called _x_

Phyllitic

If the minerals are barely visible to the naked eye, their alignment results in an obvious but not very well-defined foliation. This type of texture is called _x_

Schistose

If the minerals are visible to the naked eye, their layering is more distinct and results in a texture called _x_. These types of rocks are usually composed of platy materials like chlorite, graphite, biotite, and muscovite.

Gneissic

If the minerals are visible and elongated, the rock exhibits a coarsely branded appearance due to the alignment of minerals like amphibole, feldspar, and quartz. This type of texture is called _x_

Crystalline textures

result when the parent rock is exposed with enough heat that it induces recrystallization of the existing minerals.

Crystalline

_x_ metamorphic rocks are usually composed only of one type of mineral.

Metamorphic rocks

are mostly composed of minerals that only form at the high temperatures and pressures associated with the process of metamorphism.

Index minerals

They aid in the identification of metamorphic rocks as well as the temperature and pressure when it was formed.

Mineralogist

person who specialized in the study of the chemistry, crystal structure, and physical and optical properties of minerals.

Ores

are naturally-occurring materials that can be profitable mined. It can be mineral or rock or metallic or nonmetallic, depending on the economic requirement.