Minerals

What is a mineral? Naturally occurring inorganic (no living thing or remains) Solid Definite shape ( arranged in an orderly pattern) definite chemical composition

Is it inorganic? Coal? No, it is not a mineral- How is it made? magnetite Yes, a mineral pearl No, not a mineral- How is it made?

Does it occur naturally? Quartz yes, a mineral- one of the last minerals to form from a magma chamber. Silver yes, a mineral steel no, not a mineral- How is it made?

Solid in crystalline form? Petroleum no, not a mineral- What is its natural form? mercury glass not a mineral- What is its form? amorphous

Definite chemical composition? Calcium yes, Ca a mineral Graphite yes, C Concrete no, not a mineral- Why?

Rock forming minerals Over 3000 minerals only 20 are common, these are rock forming minerals two main groups- silicates and nonsilicates

Silicates 96% of the crust contain silicon (Si) and Oxygen (O) Feldspars are the most common silicate minerals, contain Ca, K, and Na Examples- Orthoclase and plagioclase Ferromagnesium- contain Fe and Mg

Nonsilicates 4% of the crust No silica Six major groups carbonates-ex. Calcite halides- ex halite native elements- Made of one element ex. copper and silver oxides- hematite and corundum sulfates- gypsum sulfides- galena, pyrite

Crystal Structure Specific geometric arrangement of atoms or ions Crystal = natural solid with a definite shape Can be seen under microscope or with the aid of x rays

Identifying Minerals Characteristics of Minerals Each mineral has specific properties that provide useful clues for identifying minerals. Optical properties- properties will be identified by looking at the mineral. Tests- tools are used to run tests on the mineral.

Optical Properties Color Most easily observed ex. Sulfur is bright yellow, azurite is deep blue least reliable characteristic quartz consists of many colors weathering may hide true color

Luster metallic luster- like polished metal like silver Light reflected from the surface of a mineral metallic luster- like polished metal like silver All others are non metallic vitreous luster- reflects like glass pearly luster adamantine- brilliant luster ex. Diamond or gems other lusters include: waxy, greasy, dull, earthy

Crystal Shape Regularly shaped particles, or pattern. Most crystal shapes are hard to identify. six crystal systems cubic ex. Halite, Pyrite orthorhombic ex. Sulfur tetragonal ex. Chalcopyrite hexagonal ex. Plagioclase, Orthoclase monoclinic ex. Micas triclinic ex. Kyanite

Cleavage The tendency to split along certain flat surfaces and is related to types of bonds ex. Mica (general name) splits easily in one direction, it has one perfect cleavage ( splits in parallel sheets) Example- biotite and muscovite

Fracture Some minerals do not break along cleavage planes instead they fracture or break unevenly into curved or irregular pieces splintery or fibrous fracture- looks like pieces of broken wood conchoidal- curved surfaces like the inside of a shell Chapter 3 &4 Minerals What is a mineral? Naturally occurring inorganic (no living thing or remains) solid definite shape ( arranged in an orderly pattern) definite chemical composition Is it organic? Coal? Yes, not a mineral magnetite no, a mineral pearl yes, not a mineral Does it occur naturally? Quartz yes, a mineral Silver steel no, not a mineral Solid in crystalline form? Petroleum natural gas mercury glass not a solid, amorphous Definite chemical composition? Calcium yes, Ca a mineral Graphite yes, C concrete Rock forming minerals Over 3000 minerals only 20 are common, these are rock forming minerals Quartz, orthoclase,plagioclase, muscovite, biotite, calcite, dolomite, halite, gypsum, olivine, pyroxine, amphibole two main groups- silicates and nonsilicates Silicates 96% of the crust contain silicon (Si) and Oxygen (O) Feldspars are the most common silicate minerals, contain Ca, K, and Na Ferromagnetism- contain Fe and Mg Nonsilicates 4% of the crust No silica Six major groups carbonates-ex. Calcite halides- ex halite native elements- copper and silver oxides- hematite and corundum sulfates- gypsum sulfides- galena, pyrite Crystal structure Specific geometric arrangement of atoms or ions crystal= natural solid with a definite shape can be seen under microscope or with the aid of x rays. Silicates are tetrahedrons and may be single chain, double chain, or sheets Identifying Minerals Characteristics of Minerals each mineral has specific properties that are the result of its chemical composition and crystal structure. These properties provide useful clues for identifying minerals. Some properties will be identified by looking at the mineral other properties will be determined by simple tests Color Most easily observed ex. Sulfur is bright yellow, azurite is deep blue least reliable characteristic quartz consists of many colors weathering my hide true color Luster Light reflected from the surface of a mineral metallic luster- like polished metal all others are non metallic vitreous luster- reflects like glass pearly luster adamantine- brilliant luster ex. Diamond other lusters include: waxy, greasy, dull, earthy Crystal Shape Regularly shaped particles, or patterns most crystal shapes are hard to identify six crystal systems cubic ex. Halite, pyrite orthorhombic ex. Sulfur tetragonal ex. chalcopyrite hexagonal ex. Plagioclase, orthoclase monoclinic ex. micas Streak The color of a mineral in powdered form observed by rubbing the mineral against a piece of unglazed ceramic tile called a streak plate the streak is not always the same color as the mineral mineral that have a hardness higher hat the streak plate can not be tested Cleavage The tendency to split along certain flat surfaces and is related to types of bonds ex. Mica splits easily in one direction, it has one perfect cleavage ( splits in parallel sheets) Fracture Some minerals do not break along cleavage planes instead they fracture or break unevenly into curved or irregular pieces splintery or fibrous fracture- looks like pieces of broken wood Hardness The ability to resist scratching hardness does not mean resistance to cleavage or fracture the hardness of an unknown mineral may be determined by using Mohs Hardness Scale this scale lists 10 minerals in order of increasing hardness the softest is talc with a hardness of 1 the hardest is diamond with a hardness of 10 Mohs Hardness Scale Mineral hardness common test talc 1 easily scratched by fingernail gypsum 2 can be scratched by fingernail calcite 3 barely can be scratched with a copper penny fluorite 4 easily scratched with steel file or glass Apatite 5 can be scratched by steel file or glass Feldspar 6 scratched glass with difficulty quartz 7 easily scratches steel and glass topaz 8 scratches quartz corundum 9 no simple tests diamond 10 scratched everything Testing hardness Galena scratches gypsum but not calcite, its hardness is around 2 if neither of the two minerals scratches the other, they have the same hardness

Simple Tests Streak Test The color of a mineral in powdered form observed by rubbing the mineral against a piece of unglazed ceramic tile called a streak plate the streak is not always the same color as the mineral mineral that have a hardness higher than the streak plate can not be tested

Hardness Test The ability to resist scratching hardness does not mean resistance to cleavage or fracture the hardness of an unknown mineral may be determined by using Moh’s Hardness Scale -this scale lists 10 minerals in order of increasing hardness -Softest is talc with a hardness of 1 The hardest is diamond with a hardness of 10

Moh’s Hardness Scale Mineral hardness common test talc 1 easily scratched by fingernail gypsum 2 can be scratched by fingernail calcite 3 can not scratch a copper penny fluorite 4 can easily scratch a penny Apatite 5 can barely scratch glass Feldspar 6 can scratch glass quartz 7 very easily/deeply scratches steel and glass topaz 8 scratches quartz corundum 9 no simple tests diamond 10 scratches everything

Specific Gravity The ratio of the weight of the mineral to the weight of an equal volume of water. Each mineral has its own specific gravity Can be used to identify a mineral

Acid Test Used to easily identify calcite A drop of HCl dropped onto Calcite will cause it to effervesces. The bubbles are CO2 gas. Dolomite also responds to the acid test but not as violently and only in powdered form.

Special Properties Magnetism- Can attach a magnet Fluorescence- the ability to glow under UV light ex. Calcite appears red under UV Phosphorescence- minerals that continue to glow after a UV light is removed.ex sphalerite

Special Properties con’t Double refraction- crystals that bend light in such a way that they produce a double image of any object viewed. Radioactivity- certain atoms have unstable electron or neutron arrangements. These minerals activate a Geiger counter.

End of Minerals