Rocks and Minerals Chapters 10-11

Rocks  Earth’s crust is made of rock.  Rocks are mixtures of minerals and sometimes other materials.

 When studying a rock sample, geologists observe the rock’s:  Color  Texture  Chemical composition

 Most rocks are made up of grains, particles of minerals, or other rocks.  Texture is the look that results from:  Size  Shape  Pattern of rock’s grains

 Coarse-grained-- large/easy to see.  Fine-grained – small, even microscopic.

 Grains in rock often form a pattern.

 Flat layers (strata)

 Wavy, swirling patterns

 Rows of beads

 Random or no pattern

 Some rocks have NO grain, because they cooled too quickly when they formed.

There are 3 groups of rocks:  Igneous  Metamorphic  Sedimentary

Igneous Rocks Formed from the cooling of molten (melted) rock. Examples: pumice, granite, basalt

Sedimentary Rocks Formed when particles of other rocks, plants, or animals are cemented together. Examples: Sandstone, breccia, siltstone

Formed when existing rock is changed by heat, pressure, or chemical reactions. Examples: gneiss, schist, phyllite Metamorphic Rocks

The Rock Cycle

Minerals  A mineral:  occurs naturally  Is inorganic  Is solid  Has a crystal structure  Has a definite chemical composition

Minerals  There are 3000 minerals.  100 are common.  20 minerals make up most of the rock’s of Earth’s crust (rock-forming minerals).

Mineral Formation  Minerals form through:  Crystallization of melted materials.  Crystallization of materials dissolved in water.

Crystals  Repeating patterns of a mineral’s particles that form a solid.

Minerals  All minerals contain certain elements in definite amounts.  Most minerals are compounds (two or more elements).  Silver and gold are considered minerals.

Mohs Hardness Scale The Mohs hardness scale ranks ten minerals from softest to hardest Diamond Talc 1 Gypsum 2 Calcite 3 Fluorite 4 Apatite 5 Feldspar 6 Quartz 7 Topaz 8 Sapphire 9 Diamond 10

Minerals are ranked according to:  Color

 Streak– the color of a mineral’s powder.

 Luster – how shiny a mineral is.

 Density—mass per unit volume (specific gravity)

 Cleavage – breaking of a mineral along a regular line.

 Fracture – irregular breaking of a mineral.

Fluorescence Minerals that glow under ultraviolet light.

Magnetism Magnetism occurs naturally in some minerals, such as magnetite.