Presentation on theme: "Minerals & Rocks Honors Notes. A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and a crystalline structure."— Presentation transcript:
Minerals & Rocks Honors Notes
A Mineral is a naturally occurring Inorganic Solid with a definite chemical composition and a crystalline structure.
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.)
Two Major Types of Minerals Silicate Minerals ◦Contain silicon (Si) plus oxygen (O) or silicon dioxide (SiO 2 ). ◦The most common rock-forming minerals ◦May 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, AL ◦ Plagioclase- Si, O, Ca, Na EX: Quartz composed of only Si and O ◦Make up 96% of the Earth’s crust. Earth’s oceanic crust is denser and contains a larger percentage of silicates than continental crust.
Two Major Types of Minerals (cont’d) Non-silicates ◦Contain no silicon ◦Many 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.
Physical Properties Mineral appearance Hardness Luster Specific gravity Streak Cleavage and fracture Cleavage and fracture
Mineral appearance How it looks like color What color is it? Which one of the following is gold? Identify by appearance.
Hardness A measure of how easily a mineral can be scratched Mohs Hardness Scale ◦developed in 1812 by Friedrick Mohs (an Austrian mineral expert) as a method to identify minerals.
Luster The way a mineral reflects a light. metallicnonmetallic Either metallic or nonmetallic
Specific Gravity compared The specific gravity of a mineral is the ratio of its weight compared with the weight of an equal volume of water. 19 Gold has specific gravity of times heavier It means gold is 19 times heavier than water. 19 times heavier
Streak When a mineral is rubbed across a piece of porcelain tile a streak of powdered mineral is left behind.
Cleavage Cleavage is the way that mineral breaks. Minerals that break along smooth, flat surfaces have cleavage. Mica has cleavage
and Fracture!... Mineral that breaks uneven, rough, or jagged surfaces have fracture. Quartz has fracture quartz
Atom Arrangement Some 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.
Crystal Shape – Types of Symmetry Which of these would halite be the shape of?
Plane Name 1 =Basal = Prismatic =Cubic =Rhombo- hedral
An illustration appearance:luster,color and streak
An illustration cleavage and fracture
Identify the minerals below for cleavage and fracture CLEAVAGE FRACTURE
Special Properties of Minerals Magnetic – use a magnet and see if it sticks Taste – certain minerals have a specific taste Fluorescence – glowing while under a U.V. light Phosphorescent – continues to glow after the U.V. light is off Radioactive – test minerals with a Geiger counter Double Refraction – Splits light rays into 2 parts. (see a double image) Look through the mineral for the image.
Rocks A rock is a naturally formed consolidated solid mixture made up of minerals, rock fragments, or volcanic glass Essential Minerals: always occur in the rock Accessory Minerals: sometimes occur in rock
Classify Rocks by how they form Igneous ◦- Made up of magma or lava when it cools and hardens Sedimentary ◦- Made from sediments Metamorphic ◦- Rocks changed by pressure & heat
Igneous Rocks Formed from lava or magma ◦Lava : extrusive or volcanic ◦Magma: Intrusive or plutonic (pillow-like) Intrusive Igneous rocks Formed from magma which cools and solidifies below Earth’s surface Cooling and solidification take a long time resulting in large visible crystals (coarse-grained) Extrusive Igneous Rocks Small to no mineral crystals due to faster cooling lava above Earth’s surface (fine-grained) Occurs at volcanoes or through ocean floor
Sedimentary Rocks Sedimentary Rocks Rock is a fused mixture of minerals. Some of these minerals could be in bits and pieces of other rocks. Broken into pieces (clasts) through weathering ◦Rock exposed at the surface is attacked by the weather Water: enters cracks, expands, & breaks rocks down Rain: acidic dissolves minerals Movement in rivers: collects at the bottom
Sedimentary Rocks Formation Sedimentary Rocks Formation Build very slowly in layers, until the environment changes ◦Compaction: pieces compact due to weight squeezing them together ◦Cementation: minerals acting as cement holding sediments together ◦Precipitation: water evaporates & minerals are left behind
Classifying Sedimentary Rocks Classifying Sedimentary Rocks Clastic Rocks: pieces of other rocks
NonClastic Rocks Minerals in water which evaporates to leave behind deposits (rocks) or fossil materials that compact into rock. Ex: ◦1. Limestone: calcite and seashells ◦2. Rock salt: halite ◦3. Rock gypsum: gypsum ◦4. Chert: Quartz ◦5. Coal: fossil materials
Metamorphic Rocks Form from pre-existing igneous, sedimentary, or metamorphic rocks, as a result of temperature and pressure changes 3 types of changes: 1. Rearrangement of mineral grains 2. Enlargement of crystals 3. Change in chemistry of rock
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.
Characteristics of Metamorphic Rocks FoliationNonfoliated
Hints for Identifying Rocks Igneous ◦crystals intersecting at angles ◦size of the grain Sedimentary ◦layers of rock pieces Metamorphic ◦pressure created results in lines ◦pressure and heat create grains in foliation (wavy patterns) ◦hardest of the 3 rocks
Rock Cycle Changes of rocks from one rock type to another Magma Igneous Rock cooling weathering Sediments cementation or compaction Sedimentary Rock heat & pressure Metamorphic Rock melting