Identifying MineralsIdentifying Minerals

Section 5.2Section 5.2

ObjectivesObjectivesDescribe seven physical Describe seven physical

properties that help distinguish properties that help distinguish one mineral from another.one mineral from another.

List 5 special properties that may List 5 special properties that may help identify certain mineralshelp identify certain minerals

Physical properties of mineralsPhysical properties of mineralsare a result of the chemical composition and are a result of the chemical composition and

crystalline structurecrystalline structure

Talc is highly variable, yet Sulfur is almost always Talc is highly variable, yet Sulfur is almost always yellowish.yellowish.

TalcTalc

SulfurSulfur

ColorColor: Can be very characteristic for a few minerals, but is not important for others

Talc

Luster:Luster: the way light is reflectedthe way light is reflectedeither either MetallicMetallic or or Non-metallicNon-metallic

Non-metallics are further described as:Non-metallics are further described as:

dulldull(earthy)(earthy) waxy

pearly (translucent)

glassy(transparent)

Hematite has a Hematite has a very very

red streakred streak

Streak:Streak: the color of the color of the powdered mineralthe powdered mineral

CleavageCleavage and and FractureFracturehow a mineral splits how a mineral splits oror how a mineral breakshow a mineral breaks

The Six Crystal SystemsThe Six Crystal Systems

IsometricIsometric OrthorhombicOrthorhombic

TetragonalTetragonal HexagonalHexagonal

MonoclinicMonoclinic TriclinicTriclinic

Isometric SystemIsometric System

Three axes of equal length intersect at 90 degree Three axes of equal length intersect at 90 degree angles.angles.

Examples: Galena, halite, and pyrite.Examples: Galena, halite, and pyrite.

Pyrite and HalitePyrite and Halite

Tetragonal SystemTetragonal System

Three axes intersect at 90 degree angles.Three axes intersect at 90 degree angles. Horizontal axes of equal length.Horizontal axes of equal length. Vertical axis can be longer or shorter than the other two.Vertical axis can be longer or shorter than the other two. Examples: Cassiterite, chalcopyrite, and zircon.Examples: Cassiterite, chalcopyrite, and zircon.

Cassiterite and ZirconCassiterite and Zircon

Orthorhombic SystemOrthorhombic System

Three axes of different lengths intersect at 90 Three axes of different lengths intersect at 90 degrees.degrees.

Examples: Olivine, topaz, and staurolite.Examples: Olivine, topaz, and staurolite.

Olivine (Peridot) and Topaz Olivine (Peridot) and Topaz

Hexagonal SystemHexagonal System

Three horizontal axes of the same length intersect at Three horizontal axes of the same length intersect at 60 degree angles60 degree angles

The vertical axis may be longer or shorter than the The vertical axis may be longer or shorter than the horizontal axes.horizontal axes.

Examples: Calcite, hematite, and quartz.Examples: Calcite, hematite, and quartz.

Calcite and Quartz (Amathyst)Calcite and Quartz (Amathyst)

Monoclinic SystemMonoclinic System

Three axes of different lengths, two intersect at 90 Three axes of different lengths, two intersect at 90 degree angles.degree angles.

The third axis is oblique (inclined) to the others.The third axis is oblique (inclined) to the others. Examples: Micas, gypsum, microcline (orthoclase)Examples: Micas, gypsum, microcline (orthoclase)

Gypsum and Orthoclase Gypsum and Orthoclase (Amazonstone)(Amazonstone)

Triclinic SystemTriclinic System

Three axes of unequal length that are oblique Three axes of unequal length that are oblique (inclined) to each other. No 90 degree angles.(inclined) to each other. No 90 degree angles.

Examples: Plagioclase feldspars, turquoise, and Examples: Plagioclase feldspars, turquoise, and axinite.axinite.

Moh’s Hardness ScaleMoh’s Hardness Scale

Microsoft TableMicrosoft Table

We use a scale from 1 to 10 called MOH’S We use a scale from 1 to 10 called MOH’S SCALE OF HARDNESS.SCALE OF HARDNESS.

Talc is a 1 and diamond is a 10. Talc is a 1 and diamond is a 10. Most minerals fall between 3-6. The field Most minerals fall between 3-6. The field

scale can be very helpful:scale can be very helpful:

Field Scale of HardnessField Scale of Hardness

Finger NailFinger Nail 2.5 2.5

PennyPenny 3.5 3.5

Nail or Knife 5.0 to 5.5Nail or Knife 5.0 to 5.5

GlassGlass 5.5 to 6.0 5.5 to 6.0

Specific Gravity (heft):Specific Gravity (heft):

Density = Mass/VolumeDensity = Mass/Volume

SG = Density of Sub./Density of HSG = Density of Sub./Density of H22OO

Dry weight of Mineral SG = ----------------------------------- Dry weight - weight in water

Example low and high Specific GravityExample low and high Specific Gravity

Graphite (low)Graphite (low)

Galena (high)Galena (high)

Unique Characteristics Unique Characteristics of a few mineralsof a few minerals

Magnetism:Magnetism:

Some minerals are attracted to Some minerals are attracted to a magnet.a magnet.

Magnetite

Fluorescence:Fluorescence:Minerals which will glow under Minerals which will glow under

an ultraviolet (black) light.an ultraviolet (black) light.

Minerals that continue to glow after the ultraviolet light is cut off are called phosphorescent.

Opal

Chatoyancy and AsterismChatoyancy and Asterism

Chatoyancy: Silky appearance due to large Chatoyancy: Silky appearance due to large numbers of parallel mineral fibers.numbers of parallel mineral fibers.

Asterism: Six-sided star shape when the Asterism: Six-sided star shape when the mineral reflects light.mineral reflects light.

Radioactivity:Radioactivity:

Some radioactive minerals will Some radioactive minerals will emit charged particles that are emit charged particles that are detected by a geiger counter.detected by a geiger counter.

Uranitite

Malleability:Malleability:

Some minerals Some minerals are bendableare bendable

Some minerals Some minerals are brittleare brittle

GarnetCopper

Feel:Feel:

Some minerals feel greasy or Some minerals feel greasy or soapy (unctuous)soapy (unctuous)

Graphite

Solubility:Solubility:

Some minerals are soluble (will dissolve) Some minerals are soluble (will dissolve) in waterin water

Halite

Double Refraction:Double Refraction:

Optical Optical properties reveal properties reveal a double imagea double image

Iceland Spar (Calcite)

Taste:Taste:

Some minerals taste salty.Some minerals taste salty.

Halite

React with acids:React with acids:

Carbonates react with hydrochloric acid Carbonates react with hydrochloric acid and give off COand give off CO22 gas gas

Calcite