http://www.beg.utexas.edu/mainweb/publications/graphics/granite.htm

http://en.wikipedia.org/wiki/File:USDA_Mineral_Sandstone_93c3955.jpg

http://www.gccaz.edu/earthsci/imagearchive/gneiss.htm

The diagram in the next slide represents the ROCK CYCLE—a scheme that represents the processes of continuous changes that connect the three major groups of rocks:

SEDIMENTARYIGNEOUSMETAMORPHIC

It also shows two other important parts of the “Rock Cycle” – SEDIMENTS and molten LAVA and MAGMA

Note about image sources: Many images come from a website (Volcano World) that no longer is supported, so no credit is given. The last slide provides possible sources.

A mineral isNaturally occurringInorganicDefinite chemical composition & crystalline

structureSolid

All physical properties of minerals come from the “internal arrangement of atoms”

The Color Test- easiest test to do but not always reliable

The Streak Test -The color of the powdered mineral.Performed by rubbing the unknown mineral on

an unglazed tile.The Luster Test -the way a mineral shines

or doesn't shinethe only way to really learn the different

lusters is to see them for yourself.

Metallic- looks like shiny metalNon-metallic- all the other ways that a mineral

can shineGlassy/vitreous- shines like a piece of broken glass

(most common non-metallic)Dull/earthy- no shine at allResinous/waxy- looks like a piece of plastic or dried

gluePearly- looks oily it may have a slight rainbow like

an oil slick on water. Also looks like the inside of some clam shells

Adamantine- brilliant, sparkling shine like a diamond

Hardness- a minerals resistance to scratching. This should not be confused with brittleness. A diamond is very hard and will scratch a hammer but a hammer will smash a diamond. Likewise, talc, one of the softest minerals, is not squishy. It will still put a serious hurting on you if you get hit in the head with it.

1. Talc (Softest)2. Gypsum3. Calcite4. Fluorite5. Apatite6. Feldspar (AKA Albite)7. Quartz8. Topaz9. Corundum10. Diamond (Hardest)

Choose one mineral to be the scratcher and one to be the scratchee.

Pick a smooth, flat surface to scratch. After doing the test, wipe the powder away to confirm that

the scratchee really got scratched. If the scratchee did not get scratched, switch the two rocks

and repeat. Hardness Tools

Fingernail 2.5 Penny 3.5

Iron Nail 4.5 Glass Plate 5.5

Steel File 6.5 Streak Plate 7

Cleavage -To break along flat surfaces.Examples of CleavageCubic- To break into cubesRhombihedral- to break into “pushed over

cubes” Basal- to split into thin sheets

The way a mineral without cleavage breaks.Examples of Fracture

conchoidal- to break in a scooped out bowl shape- like a conch (sea snail)

hackly fracture- to have irregular sharp edges

splintery- to break into long, thin needles

Acid- Calcite and powdered dolomite will effervesce (fizz) in dilute hydrochloric acid (HCl)

Smell- Sphalerite will give off a rotten-egg smell when streaked on a streak plate. (Note: pure sulfur does not smell like rotten eggs!)

Magnetism- Magnetite (AKA Lodestone) will pick up paper clips (weak samples will only be able to pick up staples)

Taste- Halite is rock salt and will taste salty. *Do not taste the samples since some have been tested with acid to see if it is calcite.

Fluorescence- some minerals (mostly forms of calcite) will glow in fluorescent colors under a black (UV) light.

Form by solidification (crystallization) of melted minerals

At the surface, LAVA hardens to form EXTRUSIVE rocks with tiny (FINE-GRAINED) crystals or GLASSY (no crystal) TEXTURES

Beneath the surface, MAGMA hardens to form INTRUSIVE rocks with easily visible (COARSE-GRAINED) crystal texture.

Light-colored, coarse- grained, no pattern

Mostly quartz, feldspar, mica, and hornblende

Often used for buildings and monuments

Dark-colored, fine- grained, extrusive

Formed where lava erupted onto surface

Most widespread igneous rocks

Found locally in the Palisades along west shore of Hudson River, Connecticut River valley

Dark-colored, coarse- grained intrusive

Similar composition to basalt—plagioclase feldspar with some pyroxene and olivine

Natural volcanic glassForms when lava

cools very quicklyUsually dark, but

small pieces may be clear

Fractures along curved (conchoidal) surface

Used as spear and arrow points, knives

Light colored, frothy (many air spaces)

Same minerals as in granite, but finer in grain size

Sedimentary rocks may be made of rock fragments—sediments—or by chemical reactions. The classification of sediments is shown below.

The most important of these is coal. Anthracite coal results from the greatest pressure and releases the most energy when burned. Other varieties are bituminous and lignite. “Petrified” (permineralized) wood is another organic rock.

Shale is the most common sedimentary rock

Sedimentary rocks cover about three-quarters of the land surface

For more about sedimentary rocks:

Formed by heat and pressure changing existing rocks

REGIONAL METAMORPHIC affects a large area and results from plate tectonics

CONTACT METAMORPHISM affects rocks on a local scale, such as “baking” sedimentary rocks next to magma or lava

Gneisses and schists are common in New York City and Westchester.

http://www.state.nj.us/dep/njgs/

One of the most abundant minerals in the world (Quartz and feldspar fight for #1)

Makes beach sandMakes glass (melted beach sand)- Sweet Home

AlabamaChemical formula: SiO2Since it is SiO2, there is twice as much oxygen as

silicon.Oxygen is the #1 element in the crust with Silicon

#2 (and about half that of Oxygen)Crystal shape is a pyramid called a “tetrahedron”

Tetra = 4hedron =“sided solid

There are many web sites that can provide you with more information about rocks and images. Here are a few:

http://www.gccaz.edu/earthsci/imagearchive/gneiss.htm

http://geology.about.com/library/bl/images/blrockindex.htmBibliographyDr. Michael J. Passow

http://www.mrsciguy.com/rocks.html