Mineralogy/ Petrology from usep lecture

Protons

positive (+) charge

Neutrons

no charge

Electrons

negative (-) charge

Cations

a loss of electrons, resulting in a positive (+) charge

Anions

a gain of electrons, resulting in a negative (-) charge

Crystal

a homogenous solid possessing long-range, three dimensional, internal order.

Mineral

a naturally occurring homogenous solid, with definite chemical composition and an ordered atomic arrangement. It is usually formed by inorganic processes.

Rock

is an aggregate of minerals. It can be composed of only one kind of mineral (monomineralic) or of different kinds of minerals.

Ore minerals

those minerals from which one or more metals may be extracted at a profit.

Industrial Minerals

– those minerals which are, themselves, used for one or more industrial purposes such as in the manufacture of electrical and thermal insulators, refractories, ceramics, glass, abrasives, fertilizers, fluxes, cement, and other building materials.

Gems

– those minerals which have ornamental value, and which possess the qualities of beauty, durability, rarity, fashionability and portability.

Theophrastus

first written work on minerals

Pliny

who recorded 400 years later the mineralogical thought of his time

Georgius Agricola

German physicist who published De Re Metallica on 1556 – a work that gives a detailed account of mining practices of the time and includes the first factual account of minerals.

Nicolas Steno

- law of interfacial angles

Carangeot

– invented contact Goniometer (measuring interfacial angles)

Rome de I’Lsle

made an angular measurement on crystals confirming Steno’s work. Law of the Consistency of Interfacial Angle was formulated

William Nicol

– polarizing microscope

Federov , Schoenflies & Barlow

- developed theories on mineral symmetry and order within crystals which became the foundation of X-ray crystallography

Max Von Laue, Friedrich and Knipping

X-ray Diffraction

W.H Bragg & W.L. Bragg

published the earliest crystal structure determinations

Mineralogy

The study of minerals

Mineralogist

– Someone who studies minerals, their composition, uses, and properties

Mineraloids

are specifically naturally occuring amorphous mineral with no ordered atomic structure. They lack structure and origin.

Glass

no organized molecular structure

Ionic bonding

orderly arrangement of oppositely charged ions

Covalent bonding 

electrons are shared between atoms

Metallic bonding

electrons drift around from atom to atom

good conductors of electrical current

Van der Waals bonding

sheets of covalently bonded atoms held together by weak electrostatic forces

Polymorphs

Two minerals that have the same composition but different crystal form

Pseudomorph

f a crystal of a mineral is altered so that the internal structure or chemical composition is changed but the external form is preserved.

are formed by substitution, deposition, or alteration

Nucleation

first stage of crystal growth, which implies that growth can commence only after a nucleus has been formed.

Euhedral

A crystal with well formed crystal faces.

Forms when there is sufficient space and time for the crystal to grow.

Anhedral

A crystal with poorly-formed crystal faces.

Forms when space and/or time is limited

ISOMETRIC

TETRAGONAL

ORTHORHOMBIC

MONOCLINIC

TRICLINIC

HEXAGONAL

TRIGONAL

The 6 basic crystal systems are:

Physical properties

We identify minerals by visual and chemical properties called physical properties.

Color

may be diagnostic for a few minerals, but in general, a given mineral can have a range of colors.

ROCK CRYSTAL Clear, colorless quartz

MILKY QUARTZ Translucent white quartz

ROSE QUARTZ Milky pink quartz ; color is thought to be due to various impurities (titanium, iron, manganese) or microscopic inclusions of other minerals

AMETHYST Purple quartz ; Its color is due to "holes" of missing electrons in the crystal in combination with iron impurities

CITRINE Yellow quartz ; Its color is due to iron impurities

PRASEOLITE Green quartz ; Iron impurities account for its color, too.

SMOKY QUARTZ Gray quartz ; Its color is due to "holes" of missing electrons in combination with aluminum impurities.

CAIRNGORM Brown smoky quartz MORION black smoky quartz

READ ME

Streak

The color of the pulverized powder of a mineral.

Luster

The way a mineral’s surface scatters light

Copper, silver, gold, iron

Metallic luster

Pearly, Vitreous (glassy), resinous, silky, greasy, adamantine, dull (earthy), waxy

Non metallic luster

Hardness

The measure of a mineral to resist scratching

Measured by Moh’s Scale of Hardness

Specific gravity

is the "heaviness" of a mineral. It is defined as a number that expresses the ratio between the weight of a mineral and the weight of an equal volume of water

Crystal habit

A description of a mineral’s consistent shape

Individual Crystals

Cubic 

Cube shape

Octahedral

shape like octahedrons

Tabular

Rectangular shape

Equant 

A term used to describe a minerals that have all of their boundaries of approximately equal length.

Acicular

Long, slender crystals

Prismatic

Abundance of prism faces

Bladed

Like a wedge or knife blade

Group of distinct crystals

Dendritic

tree like growths

Reticulated 

lattice like groups of slender crystals 

Radiated

radiating groups of crystals

Fibrous 

elongated clusters of fibers

Botryoidal

smooth bulbous or globular shapes

Globular

radiating individual crystals that form spherical groups

Drusy

small crystals that cover a surface

Stellated

radiating individuals that forms like star like shape

marble

granular

mica

lamellar, foliated, micaceous

actinolite

bladed

asbestos

fibrous

millerite

acicular (needlelike) and radiating

wavellite

radiating and globular

pyrolusite

dendritic

hematite

mammillated and botryoidal,

Tenacity

The resistance that a mineral offers to breaking, crushing, bending, cutting, drawing or tearing.

It is mineral's cohesiveness.

Brittle

breaks or powders easily

malleable

can be hammered into thin sheets.

sectile

can be cut into thin shavings with a knife

ductile

bends easily and does not return to its original shape (can be stretched into wires)

Flexible

bends somewhat and does not return to its original shape.

Elastic 

bends but does return to its original shape (fibrous minerals and some acicular)

Diapheneity

Is the amount of light transmitted or absorbed by a solid. It is used strictly for hand specimens because most minerals that are opaque as hand specimen becomes transparent when very thin.

Transpa

allows most light to pass through undistorted

calcite

Translucent

Light passes through but is bent and you cannot resolve images

muscovite

Opaque

no light passes through even the thinnest slice.

cinnabar

Cleavage

The tendency of a mineral to break along a plane of weakness in the crystal lattice.

Fracture

The mineral breaks in no consistent manner

Conchoidal Fracture

The tendency for a mineral to break along irregular scoop-shaped fractures that are not related to weaknesses in the crystal structure

There are other special characteristics that some minerals exhibit that allow us to identify them –

Effervescence - Acid reaction [Calcite and Dolomite (freshly broken or powdered surface): CaCO3 & Ca(Mg)CO3 ] –

Magnetism [Magnetite: Fe3O4 ] – Salty taste [Halite: NaCl] –

Striations [Plagioclase Feldspar: NaAlSi3O8 - CaAl2 Si2O8 , Pyrite - FeS2 , Quartz - SiO2 ] –

Fluorescence - Minerals that light up when exposed to ultraviolet light, x-rays, or cathode rays – Phosphorescence - emission of light continues even after UV light is cut off

Triboluminescence - minerals gives off yellow or orange flashes when struck –

Thermoluminescence - minerals gives off a glowing light when heated

Special Characteristics

Silicates

are known as the rock-forming minerals.

Petrographic microscope

also called polarizing microscope

Refractive Index

is a measure of how much light is bent, or refracted, as it passes through the mineral

Becke Line

This technique involves slightly raising or lowering the microscope focus to observe the movement of ____ that forms near the edge of a mineral grain.