geol exam 2

Sufides

Pyrite: FeS_2

single chains of tetrahedra

Pyroxene group

Important minerals

Quartz: SiO_2 Calcite: CaCO_3 Olivine: (Mg,Fe)_2SiO_4 Plagioclase feldspar K-feldspar Micas Amphiboles Pyroxenes

rock composition

The chemical makeup of a rock, as represented by the proportions of different minerals that it contains

minerals: lots and lots of 'em

There are some 3,500 recognized minerals found on Earth.We can focus on just a few types: Silicates - Si, O combined with other cations, Carbonates - Ca, Mg and CO_3, Oxides - O^2− and metallic cations, Sulfides - S^2− and metallic cations, and Sulfates - (SO_4)^2− & metallic cations

What physical characteristics can be used to distinguish individual rock types? a. all of the possible answers are correct. b. composition c. the size and shape of grains that compose the rock d. texture

a. all of the possible answers are correct.

outcrop

an exposure of bedrock

crystalline igneous rock

an igneous rock that consists of minerals that grew when a melt solidified, and eventually interlock like pieces of a jigsaw puzzle

crystalline rock

an igneous rock that consists of minerals that grew when a melt solidified, and eventually interlock like pieces of a jigsaw puzzle

Important ions in minerals

anions charge O −2 F Cl cations charge Si +4 K +1 Ca +2 Na +1 Al +3 Mg +2 Fe +2 or +3

Which of the following statements about observing rocks at an outcrop is true? a. Clay-sized and smaller grains can be identified in the field with a hand lens. b. A hand specimen is a small piece of the outcrop that can be examined closely. c. Observing the entire outcrop does not provide important information about rock relationships and layering. d. A rock's texture cannot be characterized from a hand specimen; it can only be done in thin section.

b. A hand specimen is a small piece of the outcrop that can be examined closely.

If the black rock is igneous, like the granite, but extremely dark and fine-grained, what is a reasonable field name to give it?

basalt

mineral classes

groups of minerals distinguished from each other on the basis of chemical composition

Cleavage

how a mineral breaks

Given that a mineral has one plane of cleavage and splits into sheets, is the mineral mica, pyroxene, amphibole, halite, or calcite?

mica

Mineral Identification

mineral properties: Hardness, Cleavage, Fracture, Luster, Color, Density, Crystal habit

lava

molten rock that has flowed out onto the Earth's surface

intrusive igneous rock

rock formed by the freezing of magma underground

bedrock

rock still attached to the Earth's crust

A petrographic microscope

sends transmitted polarized light through a thin section of rock.

The silica-oxygen tetrahedra is the building block of which chemical class of minerals?

silicates

silicon-oxygen tetrahedron

the SiO_4^4- anionic group, in which four oxygen atoms surround a single silicon atom, thereby defining the corners of a tetrahedron

crystal structure

the arrangement of atoms in a crystal. Anions are generally larger than cations. Structure of mineral determined largely by how the anions are arranged and how the cations fit between them.

crystal face

the flat surfaces of a crystal, formed during the crystal's growth

crystal habit

the general shape of a crystal or cluster of crystals that grew unimpeded

The genetic scheme for classifying rocks is based on

the origin of formation

fractional crystallization

the process by which a magma becomes progressively more silicic as it cools, because early-formed crystals settle out

Assimilation

the process of magma contamination in which blocks of wall rock fall into a magma camber and dissolve

Bowen's Reaction Series

the sequence in which different silicate minerals crystallize during the progressive cooling of a melt. Experimental sequence of crystallization of minerals from a gradually cooling mafic (basaltic) magma

Mineralogy

the study of minerals and their characteristics

what is a rock?

1. A naturally-occurring solid aggregate of minerals (sometimes glass). 2. Coherent - holds together 3. e.g, marble, granite, sandstone, limestone

Atoms

1. A rigid sphere about 1 angstrom (Å) in diameter - an angstrom is 10^−10 m 2. At the center of an atom is a nucleus that contains most of the mass of the atom a. Protons with a positive charge b. Neutrons with no charge - neutral 3. Negatively charged electrons are found surrounding the nucleus

Mineral Formation

1. Crystallization from a magma 2. Crystal growth in the solid state 3. Precipitation from solution

hand specimen

A piece of rock, about the size of a fist, that can be collected for study

covalent bonding

1. Electrons shared between atoms 2. Much more stable than ionic bonds

Identify the statement that is true about a reservoir. 1. It is a component in the Earth System that holds material for a period of time. 2. A reservoir of metamorphic rock needs the addition of heat and pressure in order to change into a reservoir of sedimentary rock. 3. A reservoir of sedimentary rock at the bottom of the ocean is called eclogite. 4. It must have a biological component in order to transfer materials to another reservoir.

1. It is a component in the Earth System that holds material for a period of time.

carbonates

1. Second most abundant group in the Earth's crust 2. Major component of limestone 3. Three major minerals: Calcite: CaCO_3, Aragonite: CaCO_3, and Dolomite: (Ca,Mg)CO_3

Ions

1. When an atom loses or gains an electron to or from another atom it is called an ion. 2. Positively charged ions (loss of electron) are called cations. 3. Negatively charged ions (gain of electron) are called anions.

Ionic Bonding

1. ions of opposite charges attracted 2. (total charge must add to zero) 3. 90% of minerals are essentially ionic compounds

thin section

A 3/100-mm-thick slice of rock that can be examined with a petrographic microscope.

metamorphic foliation

A fabric defined by parallel surfaces or layers that develop in a rock as a result of metamorphism; schistocity and gneissic layering are examples.

gem

A finished (cut and polished) gemstone ready to be set in jewelry.

mineral

A homogenous, naturally occurring, solid inorganic substance with a definable chemical composition and an internal structure characterized by an orderly arrangement of atoms, ions, or molecules in a lattice. Most minerals are inorganic.

crystal

A single, continuous piece of a mineral bounded by flat surfaces that formed naturally as the mineral grew.

Crystalline Material

A substance in which atoms are arranged in a crystalline lattice.

Dike

A tabular (wall-shaped) intrusion of rock that cuts across the layering of country rock.

Equant

A term for a grain that has the same dimensions in all directions.

double chains of tetrahedra

Amphibole group

Atomic Structure

Chemical characteristics of elements determined largely by number of protons # of protons = atomic number (A) # of neutrons (N) + A = atomic mass (Z)

Abundance of the Elements (wt. %)

Crust Whole Earth Oxygen 46.3 % 29.5% Silicon 28.2% 15.2% Aluminum 8.2% 1.1% Iron 5.6% 34.6% Calcium 4.1% 1.1% Sodium 2.4% 0.6% Potassium 2.1% 0.1% Magnesium 2.3% 12.7% Titanium 0.5% 0.1% Nickel: trace 2.4% All others: trace 2.6%

sulfates

Gypsum: CaSO_4 Anhydrite: CaSO_4•2H_2O

Silica-oxygen tetrahedron

Four oxygens surrounding a silicon ion. These tetrahedra combine to make the framework of the silicates. Different combinations produce different structures.

oxides

Hematite: Fe_2O_3 Magnetite: Fe_3O_4 Spinel: MgAl_2O_4

glassy igneous rock

Igneous rock consisting entirely of glass, or of tiny crystals surrounded by a glass matrix.

sheets of tetrahedra

Mica Group

cement

Mineral material that precipitates from water and fills the spaces between grains, holding the grains together.

silicates (silicate minerals)

Minerals built from silicon-oxygen tetrahedra arranged in chains, sheets, or 3-D networks; they make up most of the Earth's crust and mantle.

Magma

Molten rock beneath the earth's surface

important mineral groups

Name Important constituents (other than O) Olivine: Si, Fe, Mg Pyroxene: Si, Fe, Mg, Ca Amphibole: Si, Ca, Mg, Fe, Na, K Micas: Si, Al, K, Fe, Mg Feldspars: Si, Al, Ca, Na, K Carbonates: C, Ca, Mg Evaporites: K, Cl, Ca, S

isolated tetrahedra

Olivine group

extrusive igneous rock

Rock that forms by the freezing of lava above ground, after it flows or explodes out (extrudes) onto the surface and comes into contact with the atmosphere or ocean.

sedimentary rock

Rock that forms either by the cementing together of fragments broken off preexisting rock or by the precipitation of mineral crystals out of water solutions at or near the Earth's surface. quartz, clay minerals, feldspar, calcite dolomite, gypsum, halite. Sedimentary rocks form layers like the pages of a book. The layers record a history of ancient events and ancient environments on the ever-changing face of planet Earth. Like a book, this history can be read by geologists. 1. 5 % by volume of the upper crust 2. 75% by area of continents 3. Often the only record of geologic events 4. a rock resulting from the consolidation of loose sediment that has been derived from previously existing rocks and accumulates in layers. (clastic, detrital, or terrigenous) 5. a rock formed by the precipitation of minerals from solution by either organic or inorganic processes (biochemical & chemical) 6. A rock formed by the consolidation of organic material (organic) 7. Rocks formed by consolidation of pieces of previously-existing rocks 8. Chemical precipitation from solution

igneous rock

Rock that forms when hot molten rock (magma or lava) cools and freezes solid. quartz, feldspar, mica, pyroxene, ampilbole, olivone

metamorphic rock

Rock that forms when preexisting rock changes into new rock as a result of an increase in pressure and temperature and/or shearing under elevated temperatures; metamorphism occurs without the rock first becoming a melt or a sediment. quartz, feldspar, mica, garnet, pyroxene, staurolite, kyanite

clastic rock

Sedimentary rock consisting of cemented-together detritus derived from the weathering of preexisting rock.

Color

The characteristic of a material due to the spectrum of light emitted or reflected by the material, as perceived by eyes or instruments.

biogenic minerals

Substances that originated within living organisms.

Obsidian is a volcanic glass that forms when lava cools very quickly and consists of a solid mass of glass through and through. Why is obsidian not classified as a mineral?

The atoms or molecules in obsidian do not have a crystalline structure.

streak

The color of the powder produced by pulverizing a mineral on an unglazed ceramic plate.

facet

The ground and polished surface of a gem, produced by a gem cutter using a grinding lap

partial melting

The melting in a rock of the minerals with the lowest melting temperatures, while other minerals remain solid. Occurs when some of the minerals forming a rock melt at lower temperatures than other minerals within the same rock

What would be the significance of finding a precipitated mineral on another planet?

The planet may have or have had liquid water on it.

Which of the following is a characteristic of all rocks?

They are a collection of minerals or a body of glass.

Gems like this diamond have smooth, reflective faces called facets. Which of the following best describes the origin of these surfaces?

They are produced by grinding and polishing.

flood basalt

Vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has low viscosity.

Laccolith

a blister-shaped igneous intrusion that forms when magma injects between layers underground in a manner that pushes overlying layers upward to form a dome. Magma that cannot spread laterally accumulates in a blister-shaped intrusion called a laccolith.

rock

a coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass

inequant

a general adjective indicating that the dimensions of an object are not the same in all directions; for example, an object that is longer than it is wide is inequant

Mohs hardness scale

a list of ten minerals in a sequence of relative hardness. with which other minerals can be compared

Hardness

a measure of the relative ability of a mineral to resist scratching; it represents the resistance of bonds in the crystal structure from being broken

gemstone

a mineral that has special value because it is rare and people consider it beautiful

specific gravity

a number representing the density of a mineral, as specified by the ratio between the weight of the volume of the mineral and the weight of an equal volume of water

Photomicrograph

a photograph of a thin section taken through a microscope

large igneous province (LIP)

a region in which huge volumes of lava and/or ash erupted over a relatively short interval of geologic time. Large areas of mafic melt that appear periodically over geologic time. LIPs result from mantle plumes at the base of the lithosphere that create huge volumes of low-viscosity mafic magmas. Lava flows cover large areas and can accumulate in thick piles.

fragmental igneous rock

a rock consisting of igneous chunks and/or shards that are packed together, welded together, or cemented together after having solidified

glass

a solid in which atoms are not arranged in an orderly pattern

magma chamber

a space below ground filled with magma

Batholith

a vast composite, intrusive, igneous rock body up to several hundred km long and 100 km wide, formed by the intrusion of numerous plutons in the same region. A batholith is a group of plutons that covers a large area.

Which type of silicate has the greatest proportion of oxygen atoms shared by pairs of adjacent tetrahedra?

framework silicates

Which statement(s) is true about igneous rocks? a. They may form from lava. b. They were molten and have frozen into a solid form. c. They may form around volcanoes. d. all of the possible answers are correct.

d. all of the possible answers are correct.

Minerals are the building blocks of our geological world. Select the features that are true of all minerals.

definable chemical composition, inorganic, crystalline solid, and naturally occurring

3-D frameworks of tetrahedra

feldspar group

The texture produced when minerals within a metamorphic rock are layered parallel to each other, as shown by the red line, is called

foliation

The hardness of a mineral is determined by

its ability to resist being scratched by other substances.

bedding

layering or stratification in sedimentary rocks

Luster

the way a mineral surface scatters light

polymorphs

two minerals that have the same chemical composition but a different crystal lattice structure. e.g., diamond and graphite andalusite, kyanite, and sillimanite