Rocks

Question 1

THE ROCK CYCLE

Answer 1

Rocks are naturally occurring combinations or coherent aggregates of minerals, fossils or other hard materials. They are classified by the way in which they form. The three rock types are:
Igneous
Sedimentary
Metamorphic
All rocks on Earth are locked into a system of cycling and re-cycling known as the ROCK CYCLE.

Question 2

IGNEOUS ROCKS

Answer 2

IGNEOUS ROCKS are “born of fire”. In other words, they were once molten and upon cooling, the magma (molten rock) crystallized into solid rock. Igneous rocks may form deep inside the Earth or at the Earth’s surface when a volcano erupts.

Question 3

(IGNEOUS ROCKS) Intrusive or Plutonic

Answer 3

Slow cooling deep beneath the Earth’s surface allows crystals to grow to large size (1/8” or more). These crystals are easily visible and distinguish this group of igneous rocks as INTRUSIVE.

Question 4

(IGNEOUS ROCKS) Extrusive or Volcanic

Answer 4

Rapid cooling near or at the Earth’s surface, produces many small crystals that are not readily seen by the unaided eye. This group of igneous rocks is called EXTRUSIVE and are typically volcanic in origin. Cooling may be so rapid that crystals do not have a chance to form and instead a glass is produced.

Question 5

Granite-intrusive

Answer 5

Graphic Granite
Porphyritic
Pegmatite Mica, feldspar

Question 6

(Granite-intrusive)PEGMATITES

Answer 6

are classified as intrusive igneous rocks, but there is a difference. They are VERY coarse grained and strictly speaking are not crystallizing out of a magma.
The coarse grained nature is the result of crystal growth in aqueous solutions rather than in the molten liquid state.
The resulting freedom of ion motion allows the crystal to grow much larger in a shorter length of time.

Question 7

Diorite - intrusive

Answer 7

DIORITE is very similar to granite, but is distinguished in the hand specimen by the absence of visible quartz.

Generally it has a salt and pepper appearance (about ½ black and ½ white).

Question 8

Gabbro - intrusive

Answer 8

GABBRO is a coarse-grained rock that is high is iron & magnesium-bearing minerals (pyroxenes, amphiboles, plagioclase feldspar, olivene). The rocks will be dark in color, somewhat heavier than granitic rocks and devoid of quartz.

Question 9

Peridotite - intrusive

Answer 9

PERIDOTITE or DUNITE is composed of 90-100% olivine. As a result it is characteristically olive-greens in color.

This material is thought to have originated in the upper mantle of the Earth.

Question 10

Rhyolite – extrusive

Answer 10

RHYOLITE’S name comes from the Greek rhyo, from rhyax, “stream of lava”. It is formed when molten rock with the same composition as a high silica granite oozes (rhyolite is VERY viscous and does not really flow) to the Earth’s surface; and therefore cools quickly so only microscopic-sized crystals develop. The volcanoes that produce rhyolite are very explosive varieties such as Mt. St. Helens, Krakatoa and O’Leary Peak (AZ). Frequently it is banded due to flow alignment of different associated minerals (quartz, feldspar, mica, and hornblende).

Question 11

Andesite - extrusive

Answer 11

ANDESITE is the fine-grained equivalent of DIORITE. It tends to be a darker gray than rhyolite and is often porphyritic, with visible hornblende.

Question 12

Basalt - extrusive

Answer 12

BASALT occurs as thin to massive lava. flows, sometimes accumulating to thicknesses of thousands of feet and covering thousands of square miles. The volcanoes that produce basaltic lavas are relatively quiet, such as the Hawaiian Islands volcanoes. Basalt is dark, fine-grained and often vesicular and amygdaloidal.

Question 13

(Basalt extrusive) Vesicular

Answer 13

They have gas pockets

Question 14

(Basalt extrusive) amygdaloidal

Answer 14

The pockets may be filled with secondary minerals, e.g quartz, zeolites minerals, calcite, opal, etc and

Question 15

(Basalt extrusive) Pahoehoe

Answer 15

is a feature that forms on the surface of very fluid basalt flows. Much like the skin on a bowl of tomato soup – the surface in contact with the air begins to crystallize, while the fluid lava below continues to flow. This drags the upper, still plastic, surface into a series of smooth wrinkles.

Question 16

Obsidian extrusive

Answer 16

OBSIDIAN is volcanic glass (an acrystalline “solid” –actually a supercooled liquid). Its glassy, lustrous and sometimes banded appearance makes it rather easy to distinguish from all other rocks. It is composed of the elements that make quartz, feldspar and iron/ magnesium minerals that have cooled so quickly that the minerals could not develop and crystallize.
Colors vary from black to red, black & red (mahogany), gray, green, iridescent, snowflake (with the silicate mineral christobalite).
Apache Tears are little nodules of obsidian.

Question 17

Perlite - extrusive

Answer 17

PERLITE is a light gray volcanic glass, having numerous concentric cracks which give rise to a perlitic or onion skin structure. It is generally of rhyolitic composition. It also exhibits a pearly luster.

Apache Tears are some times found embedded in perlite

Question 18

Pumice - extrusive

Answer 18

PUMICE is highly vesicular (i.e. it has lots of gas bubble holes) and is of rhyolitic composition.
Due to the many small holes, it is lightweight and will often float in water.

Question 19

Tuff - extrusive

Answer 19

Tuff is the accumulation of ash and small pyroclastic debris (

Question 20

Volcanic Breccia - extrusive

Answer 20

VOLCANIC BRECCIA is pyroclastic (fire-formed fragments) and forms in explosive eruptions. It is a mix of large angular fragments and small ash.
Often, the material is hot when it comes to rest and cools (welds) into a very hard rock.

Question 21

SEDIMENTARY ROCKS

Answer 21

SEDIMENTARY ROCKS are composed of particles derived from pre-existing rocks or by the crystallization of minerals that were held in solutions.

Question 22

(SEDIMENTARYROCKS)

Fragmental or Clastic

Answer 22

These sedimentary rocks show evidence of transport rounding of the grains and size sorting.

Question 23

(SEDIMENTARYROCKS)

Chemical/Biochemical

Answer 23

sedimentary rocks are the result of either precipitation of solids from solutions (like salt from water) or by organic process, like shells from marine organisms.

Question 24

Breccia-Fragmental (large pieces)

Answer 24

Its composed of large angular pieces and clay.
The name is from the Italian word for “broken stones” or “rubble”.
Many form as the result of fault movement; others form as the result of rapid and short transportation, such as landslides.

Question 25

Conglamorate-Fragmental(large pieces)

Answer 25

Composed of large rounded pieces and clay.CONGLOMERATES are very similar to breccias, but the fragments are rounded. The name is from the Latin conglomeratus for “heaped, rolled or pressed together”.
These rocks form in alluvial fans, stream beds and pebble beaches.

Question 26

Sandstone-Fragmental (small pieces)

Answer 26

The basic composition of this rock consist(cement) of silica, carbonates, clay, or iron.The enviorment you can find these rocks include beaches, sand bars, deltas and dunes.

Question 27

Shale-Fragmental (very small pieces)

Answer 27

The basic composition of this rock is silt and clay particles.The color of it is usually gray to dark red, depending on the amount of oxide.You often find them in lakes, swamps , deltas and offshore marine.

Question 28

Limestone-Chemical

Answer 28

it is composed primarily of calcite. Generally it is dense, fine-grained, and usually white to dark gray. Its most distinguishing feature is its solubility in weak hydrochloric or acetic acid accompanied by brisk effervescence.
The environment of deposition if generally warm, shallow seas. Therefore, marine invertebrate fossils are common.

Question 29

Limestone it is used for

Answer 29

• Neutralize smokestack gases.
• Used as a functional filler in products such as paint, countertops & plastics.
• The dust on chewing gum is ground limestone.
• Mild abrasive additive to toothpaste.
• Soil conditioner
• Flux in processing iron and copper ores
• Building and ornamental stone

Question 30

Chert

Answer 30

CHERT is crypto-crystalline quartz. It is often the result of the dissolution of volcanic ash and is sometimes found in extensive beds, such as the novaculite of Arkansas.
It has waxy luster, is translucent and fractures conchoidally. Chert can be any color, but extensive beds are generally white to gray.

Question 31

GYPSUM(calcium sulfate)

Answer 31

is found in geographically wide-spread deposits resulting from the evaporation of a body of water, such as ocean basin or playa lake.
It is soft (H=2) & usually white to gray. Three varieties are: Alabaster, Satin Spar and Selenite.

Question 32

Gypsum is used for

Answer 32

wallboard and plasters, as an agricultural amendment and to control the set/cure time of Portland cement.

Question 33

ROCK SALT - chemical

Answer 33

ROCK SALT  (halite – sodium chloride) is also a deposit resulting from evaporation of a marine basin or playa lake.
It has cubic cleavage and tastes salty.

Question 34

ROCK SALT is used for

Answer 34

a source of chlorine and sodium, as a food supplement, in water softeners and as a road de-icer.

Question 35

COAL - chemical

Answer 35

COAL is considered a rock, although it is not composed of minerals, but rather the decomposed remains of large volumes of vegetation that accumulated in a wet, low oxygen environment, such as a swamp or marsh.

Question 36

Coal chemical is used for

Answer 36

Fuels for example Peat, Lignite and Sub-Bituminous & Bituminous

Question 37

DIATOMITE - chemical

Answer 37

DIATOMITE, also known as diatomaceous earth, is composed of the siliceous shells of microscopic alga called diatoms. It is light weight and is generally white.

Question 38

DIATOMITE is used for as an

Answer 38

abrasive, insecticide, filtering medium, and paint “flattener”

Question 39

METAMORPHIC ROCKS 41s

Answer 39

Under the influence of heat, pressure and fluids, pre-existing rocks are modified in form and even in internal atomic structure to produce new rocks stable at the new conditions. This is done within the solid state, i.e. without melting.