Rocks & Minerals

• Mineral - a naturally occurring, inorganic solid that has a crystalline structure and a definite chemical composition

• For the Love of God

• A platinum cast of a skull from an actual person that lived between 1720 and 1810. He was a 35 year old man from Europe. The teeth are original. The skull is covered with 8,601 flawless diamonds. Cost £14 million to produce. Sold for £50 million in 2007.

• Naturally occurring: not man-made

• copper and zinc are both minerals; brass (a mixture of copper and zinc) is not a mineral

• Inorganic: not from anything that was at one time living

• gold is a mineral; coal is not a mineral

• Crystal structure: the particles line up into a regular, repeating structure

• Definite chemical composition: made up of specific elements in a set amount (Ruby = Al2O3)

• Properties of Minerals

• 1) Color - many minerals have the same color (ex. gold and fool’s gold), so color is rarely enough information to identify a mineral

• occasionally, color is enough (malachite and azurite)

• 2) Streak - the color of a mineral’s powder; tested with a streak plate

• 3) Luster - the way a mineral reflects light from its surface (ex. metallic, glassy, waxy, dull, earthy)

• 4) Density - (mass/volume) can be used to identify minerals

• (density of gold = 19.93 g/cc; fools gold = 5 g/cc)

• 5) Hardness - determined by a scratch test; a mineral can scratch any mineral softer than itself, but will be scratched by any mineral that is harder

• Mohs hardness scale ranks 10 minerals from softest to hardest

• 6) Crystal structure - shape of the mineral’s crystals

• 7) Fracture and Cleavage - the way a mineral breaks apart

• fracture: irregular break; jagged, rough surface

• Cleavage: splits easily along flat surfaces

• 8) Special properties - magnetism, fluorescence, radioactivity, reaction to acids

4th Quarter Extra Credit Opportunity

• 20 points extra credit for a package of cookies

• Due: Thursday, March 24th

For each sample:

• #

• Name

• Picture (colored)

• At least two distinguishing properties

Example:

• #11

• sulfur

• Bright yellow

• Doesn’t scratch glass

• Rock Formation - rocks are a mixture of minerals and other materials

• some rocks contain only one type of mineral; others are made of many different minerals combined together

• All minerals are rocks, but not all rocks are minerals.

• Igneous Rock - forms from cooling magma or lava

• Extrusive rock forms from lava that cools on the earth’s surface (ex. basalt, obsidian, pumice)

• Intrusive rock forms from magma that hardens beneath the Earth’s surface (ex. granite)

• Intrusive rock usually has larger grains than extrusive rock since it takes longer to cool (more time for crystals to grow)

• Igneous rocks are used as building materials because they are hard, dense, and durable

• Sedimentary Rock - forms when sediment (small, solid pieces of material that come from rocks or living things) is pressed and cemented together

• 5 steps of sedimentary rock formation:

1) Weathering - rocks are broken down into sediments by physical and chemical processes

• 5 steps of sedimentary rock formation:

1) Weathering - rocks are broken down into sediments by physical and chemical processes

2) Erosion - sediments are carried from their source

• 5 steps of sedimentary rock formation:

1) Weathering - rocks are broken down into sediments by physical and chemical processes

2) Erosion - sediments are carried from their source

3) Deposition - sediments are deposited in a new area

• 5 steps of sedimentary rock formation:

1) Weathering - rocks are broken down into sediments by physical and chemical processes

2) Erosion - sediments are carried from their source

3) Deposition - sediments are deposited in a new area

4) Compaction - sediments are squeezed together under the pressure new layers of sediment above

• 5 steps of sedimentary rock formation:

1) Weathering - rocks are broken down into sediments by physical and chemical processes

2) Erosion - sediments are carried from their source

3) Deposition - sediments are deposited in a new area

4) Compaction - sediments are squeezed together under the pressure new layers of sediment above

5) Cementation - dissolved minerals crystallize and glue particles of sediment together

• 3 Types of Sedimentary Rocks

• Clastic Rock forms when rock fragments are squeezed together; the fragments can be very small or quite large

• ex. shale (from clay), sandstone, conglomerate (rounded rocks), and breccia (rock fragments with sharp edges)

• Organic Rock forms when the remains of plants and animals are deposited in thick layers

• ex. coal (from swamp plants) and limestone (from coral and shells)

• Chemical rock forms when minerals dissolved in solution crystallize (water evaporates or minerals precipitate out of solution)

• ex. rock salt, some limestone

• Sedimentary rocks are also used as building materials

(Sandstone)(Limestone)

• Metamorphic Rock - forms from an existing rock changed by extreme heat and pressure deep within Earth’s crust

• Foliated rocks have mineral grains arranged in parallel layers or bands

• ex. gneiss (from granite), slate (from shale)

• Nonfoliated rocks have mineral grains arranged randomly

• ex. quartzite (from sandstone), marble (from limestone)

• Metamorphic rocks are important materials for building and sculpture

• The Rock Cycle - a series of processes that slowly changes rock from one kind to another

• Fossils - the preserved remains or traces of living things; usually found in sedimentary rock

• most fossils form when living things die and are buried by sediments

• the sediments slowly harden into rock and preserve the shape of the organism

• Types of Fossils –

• Mold and cast: a mold is a hollow area in the sediment in the shape of a dead organism; a cast is a solid copy of an organism’s shape, formed when minerals seep into the mold

• petrified fossil - forms when minerals replace all or part of an organism (ex. petrified wood)

• carbon film - an extremely thin coating of carbon on rock

• trace fossils - provide evidence of the activities of prehistoric organisms - ex. dinosaur footprint

• preserved remains - actual remains of an organism encased in tar, amber, or ice which prevent the organism from decaying fully (ex. mosquito, woolly mammoth)

• Paleontologist – a scientist who studies fossils

• Relative Age of Rock - the age of a rock compared with other rocks

• Law of Superposition - in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it

• Unconformity - a place where an old, eroded rock surface is in contact with a new rock layer; caused by erosion, faults, and folding

• Index fossils - if the same type of fossil is found in rock layers in different areas, those layers are the same age

• an index fossil must be widely distributed and represent a type of organism that existed only briefly

• 6 cookie maximum per person

• Do not insult any cookie (and therefore the person who brought it)

• Allergies? Check the package for ingredients

• Draw/write neatly; be detailed

• Clean up when you have finished

• Lab is due at the end of class

Hints for Classifying Cookies

• IgneousInter-grown CrystalsBubblesGlassy

• SedimentaryLayersFossilsFragments

• MetamorphicWarped/DistortedDenseFoliation/Bands

Rock Examples

• IgneousGranitePumiceObsidian

• SedimentarySandstoneLimestoneConglomerate

• MetamorphicMarbleSlateGneiss