 Most buildings stones are rock-forming minerals, such as quartz, feldspar, mice or calcite  Is a mixture of such minerals, rock fragments, volcanic glass, organic matter or other natural materials  3 types of rocks 1. Igneous 2. Metamorphic 3. Sedimentary

 Rocks change through processes slowly over time  Sedimentary rock changes by heat and pressure to form a metamorphic rock  Metamorphic rock melts and cools to form an igneous  Magma cools to form igneous rock  Sediments are compacted into sedimentary rock

 Over time igneous rocks can be changed into sediments by weathering and erosion  Rock cycle processes neither create or destroy matter (principle of conservation of matter)  first recognized by James Hutton in the late 18 th century

 Igneous rock comes from hot magma that has been cooled  Magma comes from deep below Earth’s surface  Rocks melt deep below Earth’s surface from the pressure and temperature there  Temperature of magma ranges from 650˚ C to 1,200 ˚ C  Heat that melts rocks comes from the decay of radioactive elements

1. Intrusive Rocks  Are rocks that form from magma below Earth’s surface  Form as magma cools and mineral grains grow together  Are only found on the surface after layers of rock and soil that covered them have been removed by erosion  It takes a long time for them too cool, therefore mineral grains are large

2. Extrusive Rock  Are formed as lava cools on the Earth’s surface  Exposed to air and water, causing the lava to cool quickly  Quick cooling forms small mineral grains

 Igneous rocks are first classified as intrusive or extrusive  Further classified by the magma from which they form  3 forms: 1. Basaltic Rocks  Dense dark-colored rocks  Form from magma that is rich in iron and magnesium and poor in silica  Magma flows freely from volcanoes in Hawaii

2. Granitic Rocks  Light colored rocks  Lower density than basaltic rocks  Magma is thick and stiff  Contains lots of silica, lesser amounts of iron and magnesium  Magma builds up a great deal of gas pressure and causes violent volcanic eruptions

3. Andesitic Rocks  Mineral compositions are between basaltic and granitic rocks  Volcanoes that erupt andesitic magma can be violent

 Rocks that have changed because of changes in temperature and pressure and hot fluids  Can form from igneous, sedimentary or other metamorphic rocks  2 processes that form metamorphic rocks

1. Heat and Pressure  Rocks under Earth’ surface are under great pressure and temperature  Depending on the amount of pressure and temperature applied, one type of rock can change into several different metamorphic rocks  Metamorphic rocks can come from several kinds of parent rocks  Ex: slate can change into phyllite then schist, and finally gneiss

2. Hot Fluids  Fluids, which are water mixed with dissolved elements, react chemically with rocks  This changes the rock’s composition  This heat from the fluid changes the rocks during metamorphic processes

 Classified according to its composition and texture  2 classifications 1. Foliated Rocks  mineral grains line up in parallel layers  Ex: Slate › Forms from sedimentary rock shale › Arranged into layers when exposed to heat and pressure › Water can’t pass between the layers easily › Ideal for paving around pools and patios

› Useful for roofing and tiling  Ex: Gneiss › Forms when granite and other rocks are changed › Foliation shows up as alternating light and dark bands › Dark minerals-biotite mica › Light minerals-quartz and feldspar

2. Nonfoliated Rocks  Mineral grains grow and rearrange  Do not form layers  Ex: quartzite › Parent rock sandstone › Composed mostly of quartz grains that changes from a lot of pressure and heat › Quartz grows in size and becomes interlocking  Ex: Marble › parent rock limestone › Composed of calcite › Used by artists for sculptures because it is not as hard

 75% of exposed rocks are sedimentary  Sediments are loose materials such as rock fragments, mineral grains and bits of shell  Sediments come from already existing rocks that are weathered and eroded  Sedimentary rocks form when sediments are pressed and cemented together or when minerals form from solutions  Form as layers-older layers are on the bottom

 Sometimes forces within Earth overturn layers of rocks and the oldest are no longer on the bottom

 Are classified by their composition and by how they formed  3 classifications: 1. Detrital Sedimentary Rocks  Detritus-means wears away  Made from the broken fragments of other rocks  Weathering breaks the rock into smaller pieces  Erosion moves sediments and causes them to layer on top of one another

 Pressure from the top layers causes small sediments to stick together and form a solid rock  large sediments are cemented together by minerals quartz and calcite  named according to the shapes and sizes of the sediments that form them  Sizes: Clay, silt, sand, gravel (see table 2 Pg 105)  Shapes: › Conglomerate-sediments are rounded › Breccia-sediments have sharp angles

2. Chemical Sedimentary Rocks  Form when dissolved minerals come out of a solution  Not made from pieces of pre-existing rocks  Ex: Limestone › Calcium carbonate comes out of a solution as calcite › its crystals grow together to form limestone › Usually found on the bottom of lakes or shallow seas

 Ex: Rock Salt › Water, rich in dissolved salt evaporates and deposits halite › Halite forms rock salt › It is mined to use in the manufacturing of glass, paper, soap and dairy products › Processed and used as table salt

3. Organic Sedimentary Rock  Made of the remains of once-living things  Ex: Most common is fossil-rich limestone  Mostly contains remains of once-living ocean organisms, instead of only calcite  Shells cement together to form limestone  Coquina-made completely of shell fragments  Ex: chalk-made of microscopic shells  Ex: coal-forms when pieces of dead plants are buried under other sediments in swamps