2 A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and a crystalline structure.
3 Lets put that in a list format: 1. Minerals are a naturally occurring substance.2. Minerals are solids.3. Minerals have a definite chemical composition.4. The atoms that make up minerals are arranged in an orderly pattern (They form crystals).5. Minerals are inorganic. (They were never alive.)
4 Two Major Types of Minerals Silicate MineralsContain silicon (Si) plus oxygen (O) or silicon dioxide (SiO2).The most common rock-forming mineralsMay contain one or more other elements with the silicon and oxygen.EX: Feldspars are formed depending on what else combines with the silicon and oxygen.Orthoclase- Si, O, K, ALPlagioclase- Si, O, Ca, NaEX: Quartz composed of only Si and OMake up 96% of the Earth’s crust.Earth’s oceanic crust is denser and contains a larger percentage of silicates than continental crust.
6 Two Major Types of Minerals (cont’d) Non-silicatesContain no siliconMany important mineral groups are not silicates.Non-Silicate Minerals include: carbonates, (limestone, marble) oxides (hematite), halides (halite/rock salt), sulfides (pyrite), sulfates (gypsum), and native metals (gold, silver, copper).The non-silicate groups are a source of many valuable ore minerals and building materials.To be an ore, a mineral must occur in large enough quantities to be economically recoverable.
9 Physical Properties Mineral appearance Hardness Luster Specific gravityStreakCleavage and fracturePhysical Properties
10 Mineral appearance How it looks like What color is it? Which one of the following is gold? Identify by appearance.
11 Hardness A measure of how easily a mineral can be scratched Mohs Hardness Scaledeveloped in 1812 by Friedrick Mohs (an Austrian mineral expert) as a method to identify minerals.
12 Luster The way a mineral reflects a light. Either metallic or nonmetallic
13 Specific GravityThe specific gravity of a mineral is the ratio of its weight compared with the weight of an equal volume of water.Gold has specific gravity of 19It means gold is 19 times heavier than water.19 times heavier
15 StreakWhen a mineral is rubbed across a piece of porcelain tile a streak of powdered mineral is left behind.
16 Cleavage Cleavage is the way that mineral breaks. Minerals that break along smooth, flat surfaces have cleavage.Mica has cleavageCleavage
17 and Fracture!...Mineral that breaks uneven, rough, or jagged surfaces have fracture.Quartz has fracturequartz
18 Atom ArrangementSome physical properties are controlled by the orderly arrangement of atoms in a mineral’s structure.The arrangement of atoms and the bonds between them can reflect the way a mineral breaks, how hard it is, and what types of crystal shape it has.
19 Crystal Shape – Types of Symmetry Which of these would halite be the shape of?
23 Identify the minerals below for cleavage and fracture
24 Special Properties of Minerals Magnetic – use a magnet and see if it sticksTaste – certain minerals have a specific tasteFluorescence – glowing while under a U.V. lightPhosphorescent – continues to glow after the U.V. light is offRadioactive – test minerals with a Geiger counterDouble Refraction – Splits light rays into 2 parts. (see a double image) Look through the mineral for the image.
25 RocksA rock is a naturally formed consolidated solid mixture made up of minerals, rock fragments, or volcanic glassEssential Minerals: always occur in the rockAccessory Minerals: sometimes occur in rock
26 Classify Rocks by how they form Igneous- Made up of magma or lava when it cools and hardensSedimentary- Made from sedimentsMetamorphic- Rocks changed by pressure & heat
27 Igneous Rocks Formed from lava or magma Intrusive Igneous rocks Lava : extrusive or volcanicMagma: Intrusive or plutonic (pillow-like)Intrusive Igneous rocksFormed from magma which cools and solidifies below Earth’s surfaceCooling and solidification take a long time resulting in large visible crystals (coarse-grained)Extrusive Igneous RocksSmall to no mineral crystals due to faster cooling lava above Earth’s surface (fine-grained)Occurs at volcanoes or through ocean floor
29 Sedimentary RocksRock is a fused mixture of minerals. Some of these minerals could be in bits and pieces of other rocks.Broken into pieces (clasts) through weatheringRock exposed at the surface is attacked by the weatherWater: enters cracks, expands, & breaks rocks downRain: acidic dissolves mineralsMovement in rivers: collects at the bottom
30 Sedimentary Rocks Formation Build very slowly in layers, until the environment changesCompaction: pieces compact due to weight squeezing them togetherCementation: minerals acting as cement holding sediments togetherPrecipitation: water evaporates & minerals are left behind
31 Classifying Sedimentary Rocks Clastic Rocks: pieces of other rocks
32 NonClastic RocksMinerals in water which evaporates to leave behind deposits (rocks) or fossil materials that compact into rock.Ex:1. Limestone: calcite and seashells2. Rock salt: halite3. Rock gypsum: gypsum4. Chert: Quartz5. Coal: fossil materials
33 Metamorphic RocksForm from pre-existing igneous, sedimentary, or metamorphic rocks, as a result of temperature and pressure changes3 types of changes:Rearrangement of mineral grainsEnlargement of crystalsChange in chemistry of rock
34 Characteristics of Metamorphic Rocks Foliation: Foliated textures in metamorphic rocks have lots of layers or bands.Non-Foliated: metamorphic textures include rocks whose grains are in more random orientations. (no bands)Tend to have random crystal orientation and uniform grain size.Mineral grains tend to grow larger as metamorphism increases.
35 Characteristics of Metamorphic Rocks Foliation Nonfoliated
36 Hints for Identifying Rocks Igneouscrystals intersecting at anglessize of the grainSedimentarylayers of rock piecesMetamorphicpressure created results in linespressure and heat create grains in foliation (wavy patterns)hardest of the 3 rocks