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: SEDIMENTARY IGNEOUS METAMORPHIC 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 is Naturally occurring Inorganic Definite chemical composition & crystalline structure Solid 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 shine the only way to really learn the different lusters is to see them for yourself.

Metallic- looks like shiny metal Non-metallic- all the other ways that a mineral can shine Glassy/vitreous- shines like a piece of broken glass (most common non-metallic) Dull/earthy- no shine at all Resinous/waxy- looks like a piece of plastic or dried glue Pearly- 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. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Feldspar (AKA Albite) 7. Quartz 8. Topaz 9. Corundum 10. 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 Cleavage Cubic- To break into cubes Rhombihedral- 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 glass Forms when lava cools very quickly Usually 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.

One of the most abundant minerals in the world (Quartz and feldspar fight for #1) Makes beach sand Makes glass (melted beach sand)- Sweet Home Alabama Chemical formula: SiO2 Since 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 = 4 hedron =“sided solid

There are many web sites that can provide you with more information about rocks and images. Here are a few: m Bibliography Dr. Michael J. Passow