Minerals identification 4 1

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Section 1: Properties of Minerals What is a mineral? How are minerals identified?  mineral – A naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition  A substance must have all characteristics to be classified as a mineral A mineral must be/have:  Naturally Occurring  Inorganic  Solid  Crystal Structure  Definite Chemical Composition The substance must be formed by processes that occur naturally in the world Example: quartz Forms naturally when magma cools and hardens deep beneath the Earth’s surface  Materials such as cement, plastic, brick, steel, and glass all come from substances found in Earth’s crust but they are manufactured by people  Inorganic – the mineral cannot arise from materials that were once part of a living thing  Ex Coal is NOT a mineral because it is made up the remains of plants and animals  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)  Particles of the mineral line up in a pattern that repeats  The repeating pattern of the minerals particles forms a solid called a crystal  Faces – are flats sides of the crystal that meet at sharp edges and corners  Element – a substance composed of a single kind of atom  Ex Hydrogen  Compound – Two or more elements combined so that the elements no longer have distinct properties  Ex Water H20  Fracture – describes how a mineral looks when it breaks apart in an irregular way  Most minerals not split apart evenly  Geologist 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 fracture  Minerals that form rough, irregular surfaces - uneven fracture Conchoidal Fracture  Smooth and curved (called clam shell too) Quartz (SiO2 , Silicon dioxide ) Subconchoidal Fracture  Subconchoidal: Smooth and but not curved Andalusite (Al2 SiO5, Aluminum Silicate ) Uneven Fracture  Common Type Anhydrite (CaSO4, Calcium Sulfate ) Jagged Fracture  Sharp points in edges that catch on the finger when rubbed across Copper (Cu, Elemental Copper ) Splintery Fracture  Fibrous 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 Hydroxide Splintery Kyanite (Al2 SiO5, Aluminum Silicate Non-fibrous Earthy Fracture  Produces a texture similar to broken children's clay Limonite (A mixture of hydrated iron oxides)  Some minerals can be identified by special physical properties  Examples:  Magnetism      Occurs naturally in a few minerals: Magnetite Fluorescence (glows under ultraviolet light)  Scheelite Reactivity – reacts chemically to acids  Aragonite and calcite Optical properties – bends light to produce double image  Calcite Radioactivity – the process that occurs when a nucleus decays and emits alpha, beta or gamma radiation Special Properties  Fluorescence: minerals that glow in ultraviolet light Scheelite (CaWO4, Calcium Tungstate ) Under ultraviolet Special Properties  Magnetism: Acts like a magnet Magnetite (Fe3O4, Iron Oxide ) Special Properties  Electrical Quartz (SiO2 , Silicon dioxide) Special Properties  Radioactive Uraninite (UO2 , Uranium Oxide) Special Properties  Reactivity to acids Calcite (CaCO3, Calcium Carbonate ) [...]... volume of Sample C? 4 What is the density of Sample C? 5 Compare the density of Sample B to that of Sample C?  1) 50g and 10 cm3  2) 5g/cm3  3) 10 0g and 20cm3  4) 5g/cm3  5) the density of samples B and C is the same  Friedrich Mohs – An Austrian mineral expert  In 18 12 invented a test to describe the hardness of minerals  Called the Mohs hardness scale  This scale ranks minerals from softest... mass of 3 24 g and a volume of 12 0 cm3 What is its density? 3 24 g ÷ 12 0 cm3 = 2.7 g/cm3  Take a few minutes to work through the following problem with a partner - Properties of Minerals  Predicting: A piece of pyrite has a volume of 40 cm3 What is its mass? 200 g  Take a few minutes to work through the following problem with a partner 1 What is the mass of sample B? What is the volume of sample... Minerals always contain certain elements in definite proportions; most minerals are compounds example: Quartz SiO 2 One element of silicon, 2 elements of oxygen  Compounds have their own unique properties that differ from the properties of the elements that form it  Some elements that occur in nature, in pure form, that are minerals include:  Gold (Au), Silver... Properties of Minerals  To calculate the density of a mineral, divide the mass of the mineral sample by its volume  Density = Mass/Volume  For example, if a sample of olivine has a mass of 237 g and a volume of 72 cm3, then the density is  237 g/72 cm3 = 3.3 g/cm3  Take a few minutes to work through the following problem with a partner A sample of calcite has a mass of 3 24 g and a volume of 12 0 cm3... gold color  Only a few minerals can be identified using color only  Ex Malachite- always green, azurite – always blue  The streak of a mineral is the color of its powder  The streak color and the mineral color are often different  To test: rub a mineral against an unglazed tile (streak plate)  Luster – used to describe how a mineral reflects light from its surface  Minerals containing metals... 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  Color  Streak  Luster  Density  Hardness  Crystal Systems  Cleavage and fracture  Special Properties  An easily observed physical property  Color alone is not enough to make an identification  Ex... 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 - Properties of Minerals Identifying Property – Crystal Systems
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