Minerals, Igneous Rock, & Volcanoes

Minerals

• naturally occurring, inorganic, solid, with a definite chemical composition, crystalline structure

• have consistent & recognizable physical & chemical properties

How many types of minerals are there?

approximately 5,500 different types

Crystallization

• growth of a solid when constituent atoms bond together in chemical properties & and ordered arrangement

• a fluid can be a liquid, gas, or a mixture

• atoms must be close in proximity

• opposite charges allow atoms to bond in place as charges neutralize

• creates ordered arrangement of patterns

Solid Solution Series

range of composition in common silicate minerals where compositional zoning occurs

Polymorphism

minerals with same composition have different crystalline structures

Identification of minerals

• determination of characteristic physical properties

• match physical property against a key

• dependent upon chemistry & structure

Why identification is useful

• identify minerals

• determine usefulness of minerals

• delineate geological conditions under which minerals formed

Color

visible hue of a mineral

Streak

color left behind when a mineral is scraped on streak plate

Luster

• quality of the reflected light

• examples: metallic, non-metallic, vitreous (glassy), waxy

Habit

how minerals grow

Moh’s Hardness Scale Tips

numbers on minerals showing relative scratch-resistance

developed by Fredrick Mohs

Moh’s Hardness Scale in order (least to greatest)

1. talc

2. Gypsum

3. Calcite

4. fluorite

5. apatite

6. orthoclase

7. quartz

8. topaz

9. corundum

10. diamond

Fracture

mineral breaks into irregular pieces or shapes and does not have smooth or flat surfaces.

Cleavage

mineral breaks into flat, smooth planes

Specific Gravity/Heft

how heavy the mineral is

Striations

straight parallel lines on flat surface

Double Refraction

2 images are visible when looking through the mineral

Other Physical Properties

taste, smell, feel

Chemical Property

chemical test with HCl

Silicon

element “Si”

Silica

any combination of the elements silicon & oxygen

Silicatetrahedron

basic structure for silicate minerals

Silicate Minerals

• commonly called the rock forming minerals

• most common mineral on Earth

• technically oxides; geologists reserve the term “oxide” for minerals that have oxygen combined with elements other than silicon, calcium, & sulfur

Non-Silicate Minerals

• everything else

• may also form rocks

• source of many economically resources

8 most common minerals on Earth’s crust

• Plagioclase Feldspar

• Alkali Feldspar

• Quartz

• Pyroxene

• Amphibole

• Mica

• Clay

• Non-Silicates

Feldspar Info

• 92% Silicates - 8% Non-Silicates

• most common mineral

• usually light-colored

• includes striations

Nesosilicates

isolated or independent tetrahedra (no oxygen shared) 

ex: Olivine

Sorosilicates

bowtie tetrahedra (1 oxygen shared) 

ex: Epidote

Inosilicates

• chained tetrahedra

• single chained (2 oxygen shared)

  • pyroxene group

  • ex: augite

• double chained (alternating 2 or 3 oxygen shared) 

  • amphibole group

  • ex: hornblende

Phyosilicates

• sheet tetrahedra (3 oxygen shared)

• mica group

• ex: biotite & muscovite

Cyclosilicates

• ring tetrahedra (3 or 4 oxygen shared)

• ex: beryl

Tectosilicates

• framework tetrahedra (4 oxygen shared)

• ex: feldspar groups & quartz

8 most common elements on Earth’s crust (greatest to least)

• Oxygen

• Silicon

• Aluminum

• Iron

• Calcium

• Sodium

• Potassium

• Magnesium

Native Elements

comprised entirely of one element

ex: diamond (C)

Carbonates

contains CO₃ in structure

ex: calcite (CaCO₃)

Oxides

contains Oxygen, but not bonded to Si, Ca, or S

ex: hematite (Fe₂O₃)

Halides

contains Cl, Br, F, or I in structure

ex: halite (NaCl)

Sulfates

contains S not O in structure

ex: pyrite (FeS₂)

Phosphates

contain PO₄ in structure

ex: apatite (Ca₅(PO₄)₃(F, Cl, OH))

Rock

naturally occurring, consolidated material (or aggregate), usually composed of one or more minerals, but may also contain glass, fossils, organic materials, liquids

Rock Cycle

process of how one type of rocky material gets transformed into another

processes may involve interactions of geosphere with the hydrosphere, atmosphere, and/or biosphere

Magma

molten rock

underground cools slow = grows big

Lava

molten rock at or near Earth’s surface

above ground cools fast = grows fast

Sediments

pieces of rock, or other things; no size limitations

sedimentary rock

rock formed by compaction and cementation of sediments

weathering

process which disintegrate & decompose rock at or near Earth’s surface

transport

movement of weathered rock (almost by water)

deposition

when weathered rock stops moving

water table

underground water storage, crucial for human survival

metamorphic rock

rock formed by action of heat & pressure on existing rock

Most common rock?

basalt

igneous rock

rock formed by the cooling of molten rock

plutonic/intrusive

forms when magma cools slowly (underground)

volcanic/extrusive

forms when lava cools rapidly

Classification of Igneous

• texture

  • size, shape, arrangement of grains

• composition

  • chemistry, mineralogy (heat & pressure) (how deep underground)

texture types

phaneritic, porphyritic, aphanitic, glassy, pyroclastic

phaneritic

large crystals (slow cooling)

porphyritic

mixed sized crystals

aphanitic

small crystals (fast cooling)

glassy

no crystals

pyroclastic

fragmented by explosions

phenocrysts

large crystals surrounded in a groundmass of porphyritic rock

Chemistry of Igneous

silica (SiO₂) determines mineral content & color

felsic rock

>65% silica by weight & composed of light-colored minerals that are abundant in silica, aluminum, sodium, potassium

ex: granite/rhyolite

intermediate rock

silica 55% - 65% by weight

ex: diorite/andesite

mafic rock

silica 45% - 55% by weight and composed of dark colored minerals abundant in iron, magnesium, calcium

ex: gabbro/basalt

ultramafic

< 45% silica by weight and composed almost dark colored ferromagnesium minerals

ex: peridotite

Light Colored rock tips

white, clear, pink, peach, gray

Dark Colored rock Tips

black, green, gray

decompression melting

melting occurs by lowering the pressure on already hot rock

Flux Melting

addition of water vapor

water becomes reactive at high temperatures

adding heat

least common way to melt rock

evolution of magma

• chemical range of igneous rock indicates that there are a large variety of magma compositions

• partial melting

  • magma composition varies because different minerals melt at different temperature

• minerals crystallize in a predictable order over a large temperature range

  • Bowen’s Reaction Series

out of equilibrium

minerals/crystals dissolve and elements melt to make new minerals

differentiation

processes by which crystals separate from an originally homogenous magma

crystal setting

crystals are effectively removed from melt as they settle downwards

crystal flotation

crystals are effectively removed from melt as they float upwards

filter pressing

crystals are effectively removed from melt as the float upwards

assimilation

magma changes composition as it melts and assimilates adjacent rock 

magma mixing

magma composition changes as it mixes with different magma

magmatic stoping

movement of magma through Earth

shallow intrusive bodies

• igneous structures that solidified near Earth’s surface

• frequently smaller than structures that cool at a great depth

• cool more rapidly than those that form at great depth, aphanitic texture

• ex: ship rock, New Mexico

Volcanic neck

magma cooled in throat of a volcano

Dike

shallow tabular intrusive structure that cuts across or through

Sill

shallow tabular intrusive body that parallels layering in country rock

deep intrusive bodies

• igneous structures that solidified deep within Earth

• frequently larger than structures that cooled at shallow depth

  • cool more slowly than those that form at great depth, phaneritic texture

pluton

deep, large, blob-shaped structure

stack

small plutons (exposed over <100 km²)

Batholith

large plutons (exposed over >100km²)

Igneous Activity: divergent plate boundry

• as plates move apart, new crust is made

• decompression melting of the asthenosphere

• usually in oceanic lithosphere (mafic) - formation of basalt/gabbro

• if continental lithosphere (not common), magma assimilation may occur- formation of andesite/diorite or rhyolite/granite

Igneous Activity: convergent plate boundry

• combination of flux melting and adding heat by friction from movement of down going slab

• subduction zones not collision zones

• magma assimilation occurs as magma rises through lithosphere

Igneous Activity: intraplate

• magma assimilation occurs as magma rises through lithosphere

  • produces plutons or volcanoes

• oceanic lithosphere (composition mafic) basalt/gabbro

• continental lithosphere (composition felsic or intermediate)

  • granite/rhyolite or andesite/diorite

Abundance & Distribution

• mountain ranges & interior continental lowlands - granite

• exposed plutons formed in old sub zones - diorite/granite

• young, volcanic mountain ranges - rhyolite/andesite

• seafloor & oceanic crustal areas - basalt/gabbro

• upper mantle - peridotite & other ultramafic rock

atmosphere

originally created from gases released during volcanic eruptions 

hydrosphere

originally produced by condensation of volcanic water vapor

biosphere

both positively & negatively influenced by volcanism lava flows & volcanic ash weather to produce fertile soils

violent eruptions can destroy nearly all life in their paths

trigger rapid climate change & contribute to mass extinction

volcanic processes

escape of magma & other ejecta from Earth’s interior

ejecta

3 major categories: solid, liquid, gas

liquid

• lava

• magma at or near Earth’s surface