Minerals, Rocks, and The Rock Cycle 22.2, 22.3

Minerals and Rocks A rock is a solid combination of minerals or mineral materials A mineral is: Inorganic (not from living things) Solid Has a crystalline structure Characteristic chemical composition Building blocks of rocks

Classification Minerals are classified by: Crystal structure; their geometric shape Color Streak; color of its powder Luster; ability to reflect light Density; mass/volume Hardness; ability to avoid scratching Fracture; how it breaks Cleavage; type of fracture Others include ability to dissolve in acid, electrical properties, light refraction

Mohs Hardness Scale Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond

Igneous Rocks Form from magma Magma that flows from volcanoes is called lava Form when rock cools and solidifies Intrusive rocks cool inside the Earth, cool slowly making large crystals Extrusive rocks cool outside the Earth, cool rapidly

Intrusive Rocks Gabbro, Granite

Extrusive Rocks Obsidian, Basalt

Sedimentary Rock Weathering breaks down the Earth into smaller pieces called sediment Sediment comes from living organisms or rock Sedimentary rocks form over time when sediment is squeezed and cemented together Pressure causes the sediments to compress

Clastic Rock Sedimentary rock that forms when other rocks break and fracture Classified by size of particle which range from pebble size to boulders Conglomerate rocks contain gravel and pebbles and pieces are rounded Breccia is composed of sharp rock fragments

Conglomerate, left Breccia, right

Chemical Rock Form when rock precipitates out of a solution Rain falls and dissolves rock, the minerals are carried in streams, eventually the streams can evaporate leaving new rock behind, or the sediments settle forming limestone Typically found in dry lake beds or caves

Limestone in Lehmann Caves, Great Basin National Park, Eastern Nevada

Organic Rock Form when organisms die Shells and skeletons compress under pressure and cement to form rock

Chalk Bluff Along Truckee River Reno, Nevada

Limestone, formed on ocean floor, left Limestone in White Cliffs of Dover, England, right

Metamorphic Rock Greek for “change form” Transformed by heat, pressure, chemical reactions, and time Metamorphism can change the mineral content as new rocks become embedded in the new rock Change the texture and lead to layers Foliated rocks look like strips because the layers are parallel http://www.learner.org/interactives/rockcycle/change2.html

Gneiss Schist

Rock Type Quiz http://www.learner.org/interactives/rockcycle/types.html

The Rock Cycle http://www.learner.org/interactives/rockcycle/diagram.html

Essential Questions What are the ten most common properties that minerals are classified by? What are three groups into which rocks are classified? What are the two ways igneous rocks can form? What are the three groups of sedimentary rocks called? How are metamorphic rocks formed?

References Gabbro image www.k12.nf.ca Granite image marlimillerphoto.com Obsidian, limestone images www.geology.com Basalt image www.geologyclass.org Conglomerate www.soil-net.com Breccia flexiblelearning.auckland.a... Lehmann Caves blog.roadtrippers.com White Cliffs www.telegraph.co.uk Metamorphic rock www.earth.ox.ac.uk