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 (SiO2). 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.

Silicate Minerals Biotite Quartz Muscovite Plagioclase Feldspar

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.

Non-Silicate Minerals Pyrite Hematite Halite (salt)

Non-Silicate Minerals Gold Flourite Galena

Physical Properties Mineral appearance Hardness Luster Specific gravity Streak Cleavage and fracture Physical Properties

Mineral appearance How it looks like 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. Either metallic or nonmetallic

Specific Gravity The 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 19 It means gold is 19 times heavier than water. 19 times heavier

Specific gravity

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 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?

Name Plane =Basal 1 =Prismatic 2 3 =Cubic =Rhombo- hedral 3

An illustration appearance:luster,color and streak

An illustration cleavage and fracture

Identify the minerals below for cleavage and 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 Intrusive Igneous rocks 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 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 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 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: Rearrangement of mineral grains Enlargement of crystals 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 Foliation Nonfoliated

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 melting Magma melting cooling Metamorphic Rock Igneous Rock weathering heat & pressure Sediments Sedimentary Rock cementation or compaction