Presentation on theme: "Section 1: Properties of Minerals"— Presentation transcript:
1Section 1: Properties of Minerals Chapter 4: MineralsSection 1: Properties of Minerals
2How are minerals identified? Key Concepts:What is a mineral?How are minerals identified?
3What is a Mineral?mineral – A naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition.A substance must have all 5 characteristics to be classified as a mineral.
45 Characteristics of a Mineral A mineral must be/have:Naturally OccurringInorganicSolidCrystal StructureDefinite Chemical Composition
5Naturally occurring means: The substance must be formed by processes that occur naturally in the worldExample: quartzForms naturally when magma cools and hardens deep beneath the Earth’s surface.
6NOT naturally occurring: Materials such as cement, plastic, brick, steel, and glass all come from substances found in Earth’s crust but they are manufactured by people.
7InorganicInorganic – the mineral cannot arise from materials that were once part of a living thingEx. Coal is NOT a mineral because it is made up the remains of plants and animals
8Solid A mineral is always solid Has a definite volume and shape. Particles that make up a solid are tightly packed together, therefore they move very little (compared to the particles of a liquid)
9Crystal StructureParticles of the mineral line up in a pattern that repeats.The repeating pattern of the minerals particles forms a solid called a crystalFaces – are flats sides of the crystal that meet at sharp edges and corners
10Element – a substance composed of a single kind of atom. QUICK REVIEW: What Is the Difference Between an Element and a Compound?Element – a substance composed of a single kind of atom.Ex. HydrogenCompound – Two or more elements combined so that the elements no longer have distinct propertiesEx. Water H20
11Definite Chemical Composition Minerals always contain certain elements in definite proportions; most minerals are compoundsexample: QuartzSiO2One element of silicon, 2 elements of oxygenCompounds have their own unique properties that differ from the properties of the elements that form it.
12Definite Chemical Composition Some elements that occur in nature, in pure form, that are minerals include:Gold (Au), Silver (Ag), Copper (Cu)Listed on the periodic table
13Identifying Minerals Geologists have identified about 3,800 minerals Each mineral has characteristic properties that can be used to identify it.Some properties can be determined by looking at it, some properties require testing.
14Identifying Properties ColorStreakLusterDensityHardnessCrystal SystemsCleavage and fractureSpecial Properties
15Identifying Property- Color An easily observed physical property.Color alone is not enough to make an identification.Ex. Gold, pyrite and chalcopyrite = gold colorOnly a few minerals can be identified using color only.Ex. Malachite- always green, azurite – always blue.
16Identifying Property - Streak The streak of a mineral is the color of its powderThe streak color and the mineral color are often differentTo test: rub a mineral against an unglazed tile (streak plate)
17Identifying Property - Luster Luster – used to describe how a mineral reflects light from its surface.Minerals containing metals are often shiny.Other terms to describe luster - Earthy, waxy, and pearly.
19Identifying Property - Density Each mineral has a characteristic Density.Density – the mass in a given space or mass per unit volume.Density = mass (g)volume (cm3)Displacement – the volume of the displaced water equals the volume of the sample
20- Properties of Minerals Calculating DensityTo calculate the density of a mineral, divide the mass of the mineral sample by its volume.Density = Mass/VolumeFor example, if a sample of olivine has a mass of 237 g and a volume of 72 cm3, then the density is237 g/72 cm3 = 3.3 g/cm3
21Stop and ThinkTake a few minutes to work through the following problem with a partner.
22Practice ProblemA sample of calcite has a mass of 324 g and a volume of 120 cm3. What is its density?
27Stop and ThinkTake a few minutes to work through the following problem with a partner.
28Analyzing DataWhat is the mass of sample B? What is the volume of sample B?What is the density of Sample B?What is the mass of Sample C? What is the volume of Sample C?What is the density of Sample C?Compare the density of Sample B to that of Sample C?
29Answers 1) 50g and 10cm3 2) 5g/cm3 3) 100g and 20cm3 4) 5g/cm3 5) the density of samples B and C is the same.
30Identifying Property - Hardness Friedrich Mohs – An Austrian mineral expert.In 1812 invented a test to describe the hardness of minerals.Called the Mohs hardness scaleThis scale ranks minerals from softest to hardestA scratch test is used, a mineral can scratch any mineral softer than itself, but can be scratched by any mineral that is harder.
32Identifying Property – Crystal Systems The crystals of each mineral grow atom by atom to form the minerals crystal structure.Geologists classify these structures into 6 groups based on the number and angle of the crystal faces.These groups are called crystal systems.Example- Halite crystals are cubic. Halite crystals have 6 square faces that meet at right angles forming a perfect cube.
35Identifying Property – Crystal Systems - Properties of MineralsIdentifying Property – Crystal Systems
36Crystal systems – cleavage and fracture Cleavage – a property of a mineral that causes it to split easily along flat surfaces.Determined by the arrangement of atoms in its crystals.The arrangement of the atoms in the mineral causes the crystal to break apart more easily in one direction than another.Example- Mica separates easily in only one direction, forming flat sheets. Feldspar is another mineral that has cleavage.
38Crystal Systems – cleavage and fracture Fracture – describes how a mineral looks when it breaks apart in an irregular way.Most minerals do not split apart evenly.
39Geologist use a variety of terms to describe fracture Examples: quartz has a shell shaped (conchoidal) fracture. When it breaks, it produces curved, shell like surfaces that look like chipped glass.Pure metals like copper and iron form jagged points - hackly (jagged) fracture.soft minerals that crumble - earthy fractureMinerals that form rough, irregular surfaces - uneven fracture
43Jagged FractureSharp points in edges that catch on the finger when rubbed acrossCopper (Cu, Elemental Copper )
44Splintery FractureFibrous or finely needle shaped minerals and have a relatively stronger structure in one direction than the other two.Serpentine (Mg,Fe)3Si2O5(OH)4, Magnesium Iron Silicate HydroxideSplinteryKyanite (Al2 SiO5, Aluminum SilicateNon-fibrous
45Earthy Fracture Produces a texture similar to broken children's clay Limonite (A mixture of hydrated iron oxides)
46Identifying Properties – Special Properties Some minerals can be identified by special physical properties.Examples:MagnetismOccurs naturally in a few minerals: MagnetiteFluorescence (glows under ultraviolet light)ScheeliteReactivity – reacts chemically to acidsAragonite and calciteOptical properties – bends light to produce double imageCalciteRadioactivity – the process that occurs when a nucleus decays and emits alpha, beta or gamma radiation.
47Special PropertiesFluorescence: minerals that glow in ultraviolet lightScheelite (CaWO4, Calcium Tungstate )Under ultraviolet
48Special Properties Magnetism: Acts like a magnet Magnetite (Fe3O4, Iron Oxide )