Minerals

Mineral DefinitionA naturally occurring, inorganic solid that has a crystalline structure and a definite

chemical composition.

There are about 3,000 known mineralsOf that, 20 minerals make up most rocks

A) Minerals are Naturally Occurring:

That means that minerals must be found in nature…They aren’t man-made.

Bricks, cement, steel and glass are man-made and are not minerals.

B) Minerals are Inorganic:

Minerals contain no carbon and cannot arise out of materials that was once a part of living things.

Coal is not a mineral because it comes from the remains of living things.

C) Minerals are Solid:

Minerals have a definite volume and shape and are always a solid.

D) Minerals Have a Crystalline Structure:

The particles in a mineral have a pattern that repeats over and over to form a solid called a crystal.

The Chemical Composition of

Minerals:

A mineral always contains certain elements in definite proportions.

An element is a substance composed of a single kind of atom.

All atoms of the same element have the same chemical and physical properties.

continued Chemical Properties

Almost all minerals are compounds, where two or more elements are combined to make a new substance.

Some minerals are made up of compounds, and some minerals are made up of pure elements (or atoms of one kind).

Elements such as copper, silver and gold are considered minerals.

Physical Properties of Minerals(For Identifying Minerals)

1. Hardness

2. Color

3. Streak

4. Luster

5. Density

6. Crystal Systems

7. Cleavage and Fractures

8. Special Properties

Physical properties: 1. HardnessThis is a mineral’s resistance to being scratched This should not be confused with brittleness. A diamond is very hard and will scratch a hammer but a hammer will smash a diamond.

Mohs Scale is a scale from 1-10 that rates a mineral’s hardness. The scale goes from the softest minerals to the hardest, which is a diamond.

This is Moh’s Hardness Scale

Physical properties: 2. Color

This is the color a mineral appears to the eye.

It is not always reliable by itself, but can be used with other characteristics.

Physical properties: 3. Streak

The color of powder left when the mineral is scratched on an unglazed tile (this is the mineral’s true color)

Physical properties: 4. Luster

Luster describes a minerals appearance. Specifically, how light reflects from the mineral.

1. Metallic shines like a metal

2. Non-metallic has a glassy, earthy, or pearly appearance

Here are Some Terms Used to Describe Luster

Adamantine Transparent to translucent. Very brilliant and shiny. Example: diamond.

Dull Very low reflectivity. Like unglazed pottery.Greasy Appears to be covered with grease.Metallic Reflective and opaque. Like metal. Example:

pyrite.Pearly Similar to the inside of a sea shell.Pitchy Similar to tar Resinous Similar to honey. Example: amber Silky Similar to silk cloth.Submetallic Reflective and nearly opaque. Splinters may

be translucent Vitreous Similar to glass. Example: quartz.Waxy Appears to be covered with wax.

Physical properties: 5. Density

Density is the mass per unit volume

With minerals, we use the specific gravity (comparing a mineral’s density to the density

of water, which is a ratio and includes no units)

Physical properties: 6. Crystal Systems

Physical properties: 7. Cleavage & Fractures

Cleavage along flat surfaces

Fracture is an irregular jagged break

Conchoidal Fracture

Parallel Fractures

Physical properties: 8.Transparency

Transparency describes how well light passes through a mineral sample. There are three degrees of transparency: transparent, translucent, and opaque.

You can see objects through a transparent mineral.

You can see light, but no objects through a translucent mineral.

You can't see anything through an opaque mineral.

Special Properties of Minerals

• Magnetism is a special property of some minerals, especially magnetite. Samples are attracted by a magnet. Lodestone, a special form of magnetite, is a magnet itself.

• Double refraction - Iceland spar, the transparent variety of calcite shows double refraction.

Special Properties of Minerals

• Effervescence is a reaction to a weak acid if calcium carbonates are present.

• Electronics-grade manufactured quartz is used in a large number of circuits for consumer electronics products such as computers, cell phones, televisions, radios, and electronic games, to name just a few.

Special Property: Fluorescence

The light from ultraviolet lamps reacts with the chemicals of a mineral and causes the mineral to glow; this is called fluorescence.

If the mineral continues to glow after the light has been removed, this is called phosphorescence

Specific Minerals Next!!!

Calcite CaCO3 (carbonate)

Color: white, colorless, gray, red, brown, green, or blackStreak: white to grayishHardness: 3Specific gravity: 2.71Cleavage: perfectFracture: subconchoidalLuster: vitreous, pearly, or dullCrystal form: trigonal/hexagonalTransparency: transparent to translucentDouble refraction (You can see two images through a transparent piece of calcite.)Reacts in cool, weak hydrochloric acid.Calcite is the main mineral in limestone and forms in seawater or in the skeletons of living creatures.

Feldspar Silicate (Different forms of feldspar include combinations

of potassium, sodium, calcium, aluminum, silicon, and oxygen.)Color: white, reddish, colorless, yellow, gray, or greenStreak: whiteHardness: 6–6 1/2Specific gravity: 2.55–2.63Cleavage: perfect, right anglesFracture: uneven to conchoidalLuster: vitreous to pearlyCrystal form: noneTransparency: transparent to translucentForms in many igneous and metamorphic rocks.

Fluorite

CaF2 (halide)Color: purple, green, colorless, white, yellow, pink, red, blue, or blackStreak: whiteHardness: 4Specific gravity: 3.1–3.3Cleavage: perfect octohedralFracture: conchoidalLuster: vitreousCrystal form: cubic or octahedralTransparency: transparent or translucentForms in hydrothermal veins and around hot springs

Gypsum CaSO4•2H2O (Hydrated sulfate)

Color: colorless, white, gray, greenish, yellowish, brownish, or reddishStreak: whiteHardness: 2Specific gravity: 2.32Cleavage: perfectFracture: splintery, fibrousLuster: vitreous or pearlyCrystal form: tabular or diamond-shaped (monoclinic)Transparency: transparent to opaqueForms by evaporation around hot springs and in beds of clay

Hornblende

A combination of calcium, magnesium, iron, aluminum, silicon, and oxygen (silicate)Color: usually black, can be green or greenish brownStreak: whiteHardness: 5–6Specific Gravity: 3.28–3.41Cleavage: perfect (rhombic)Fracture: unevenLuster: silky to glassyCrystal form: monoclinic Transparency: transparent to opaqueForms in igneous and metamorphic rocks

Copper Cu (native element)

Color: copper red or pale rose redStreak: copper redHardness: 2 1/2–3Specific gravity: 8.9Cleavage: noneFracture: jaggedLuster: metallicCrystal form: cubic (but rare), usually forms dendritic or branching patternTransparency: opaqueForms in basic volcanic rocks, and in the oxygen-poor environments where sulfide minerals are deposited

Pyrite FeS2 (sulfide)

Color: pale yellowStreak: greenish blackHardness: 6–6 1/2Specific gravity: 5.0Cleavage: indistinctFracture: conchoidal to unevenLuster: metallicCrystal form: cubic, crystal faces, often striatedTransparency: opaqueGives off sparks when struck with a hard metal object. Found in igneous, metamorphic, and sedimentary rocks as an accessory mineral. May be found in hydrothermal veins. Also known as fool's gold

Hematite Fe2O3 (oxide)

Color: brownish, bright red, blood red, brownish red, steel gray, or iron blackStreak: brownish redHardness: 5–6Specific gravity: 5.26Cleavage: noneFracture: uneven to subconchoidalLuster: metallic to dullCrystal form: trigonal/hexagonalTransparency: opaqueForms from hydrothermal fluid, sometimes replacing other minerals. May also form in igneous rocks

Biotite

Composed of potassium magnesium, iron, aluminum, iron, silicon, oxygen (silicate)Color: black, dark brown, reddish brown, green, or very rarely whiteStreak: colorlessHardness: 2 1/2–4Specific gravity: 2.7–3.4Cleavage: perfect basal (pulls apart in thin sheets)Fracture: unevenLuster: vitreousCrystal form: monoclinicTransparency: transparent to nearly opaqueForms in both igneous and metamorphic rocks

Magnetite

Iron oxide (Fe3O4)Color: blackStreak: blackHardness: 5 1/2–6 1/2Specific gravity: 5.2Cleavage: noneFracture: subconchoidal to unevenLuster: metallic on freshly broken surfacesCrystal form: noneTransparency: opaqueForms in igneous rocks and in veins and replacement deposits. May be grainy. Highly magnetic

Quartz SiO2 (silicate)

Color: white, gray, red, purple, pink, yellow, green, brown, black, colorlessStreak: whiteHardness: 7Specific gravity: 2.65Cleavage: noneFracture: conchoidalLuster: vitreousCrystal form: hexagonal/trigonalTransparency: transparent to translucentOne of the most common minerals. It occurs in igneous, metamorphic, and sedimentary rocks and in mineral veins with metal ores.

A little more about Quartz:

• One of the most abundant minerals in the world (Quartz and feldspar fight for #1)

• Makes beach sand • Makes glass (melted beach sand) • Chemical formula: SiO2 • Since it is SiO2, there is twice as much oxygen as

silicon. • Crystal shape is a

pyramid called a “tetrahedron” – Tetra = 4 – hedron =“sided

solid

Rock and Mineral Definitions

• Cleavage The tendency of some minerals to break along certain planes.Crystal Habit The shape in which individual crystals grow and the manner in which crystals grow together in aggregates.Fracture The way in which a mineral breaks other than along planes of cleavage.Hardness The resistance of a minerals surface to scratching. Can be evaluated using the Mohs scale of hardness (see right column).

• Lava Magma flowing out of a volcano. Luster The manner in which a mineral reflects light.Magma Molten rock. Temperatures in the range of 700*c to 1300*c. Consists of silicon, oxygen and other minerals. Mineral A naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure.opaque A material that blocks the passage of light.Polymers Very large molecules.Silicates Minerals that contain both Si & O.

• Specific Gravity The weight of a substance relative to the weight of an equal volume of water.Streak The color of a fine powder of a mineral. Scratch a mineral sample on a streak plate to make streak.Translucent A material that permits the passage of light.Twinning 2 or more crystals that have grown together in a symmetrical wayViscosity Resistance to flow.