Geo-211 Earth Materials Exam 2

crossed polarized light (XPL)

crossed polarized light (XPL)

adding an additional polarizer called the analyzer to see different optical properties. this is generally on the top of the stage as a switch marked with an A

plane polarized light (PPL)

all microscopes have a polarizer below the stage on top of the light fixture, which only allows one direction of light to pass through

interference color

this is used to determine the birefringence of a mineral. in rotating the stage until it is furthest from extinction, at its brightest color. you choose the color near the center

birefringence

the property of some minerals that causes light to split into two rays when it passes through them. these typically show up in crystals that are hexagonal, tetragonal, and trigonal, which as uniaxial

pleochroism

some minerals will change color when the stage is rotated under PPL. it either is or isn’t and you always say what color it presents

relief

this is how distinct the mineral looks from the surroundings, and we generally look at the edges of a mineral to determine this

extinction

minerals that are not always black in XPL will typically go black every 90 degrees and we can measure the angles at which they go black.

opaque

metallic minerals are most often this. they will be solidly black in PPL or XPL.

interference figure

a figure observed with a conoscope when a section of a doubly refracting crystal is in the path traversed by convergent plane-polarized light

uniaxial

This will be a plus sign when observing the interference figure

biaxial

this will be curves at certain angles from 0 to 90 degrees when observing the interference figure

silicate

based on silicate tetrahedra (70-80% of our minerals). quartz SiO2- if there’s silicate in a mineral, it’s a silicate mineral

sulfate

sulfuric acid salts such as Barite and Gypsum

phosphate

phosphoric acid salts like Apatite

oxide

metal bonded to O2 like Cuprite

halide

contain halogen elements such as Cl, Br, F, I like Fluorite

carbonate

CO3 based like Calcite

native element

pure elements in solid form like Gold (Au)

tectosilicate

all SiO4 bonded to one another- Framework Silicates

phyllosilicate

basically Cyclo bonded together to form a flat regularly repeating structure (mica’s)

chain (ino-) silicate

a chain (single/double) of SiO4. each sharing two O with other tetrahedra- pryoxene or amphibole

nesosilicate

one SiO4 bonded to other elements

cyclosilicate

six SiO4 bonded in a ring form Si6O18

sorosilicate

two SiO4 bonded to form Si2O7 then bonded to other oxygen (sharing oxygen, which means one less)

how do we classify minerals based on composition

subclassify them based on the arrangement of tetrahedra relative to other elements

list common minerals for each subclassification of silicates

Nesosilicates: Forsterite, Fayalite, Kyanite/Andalusite/Sillimanite, Topaz. Sorosilicate’s: Epidote. Inosilicates (single-chain): pyroxenes (enstatite, ferrosilite, pigeonite, diopside, augite). Inosilicates (double-chain): amphiboles (hornblende, glaucophane). Cyclosilicates: Beryl, Tourmaline. Phyllosilicates: Talc, Illite, Chlorite, Biotite, Muscovite. Tectosilicates: Microcline, orthoclase, albite, andesine, labradorite, anorthite.

define plagioclase feldspar

two main endmembers: anorthite- Ca rich endmember (what moon is mostly made of), albite- Na rich endmember. Solid Solutions: Oligoclase, Andesine, Labradorite, Bytownite.

define alkali feldspar

Pure alkali polymorphs: orthoclase (monoclinic) and microcline (triclinic). mixed alkali with albite polymorphs: sanidine (monoclinic) and anorthoclase (triclinic). Unusual feldspars: celsian, hyalophane, buddingtonite.

define hydrolysis

the chemical breakdown of a compound and transformation of one mineral into another due to reaction with water

define ternary diagrams

we use a ternary diagram to talk about 3 component compositions

define QAPF diagram

we used a special stacked ternary diagram to talk about Igneous Rocks in particular. this is mostly for felsic and intermediate rocks. Q- quartz, A- alkali feldspar, P- plagioclase feldspar, F- feldspathoid

define biotite

microcline: tetra, sheet (brownish color)

define muscovite

define phlogopite

define kaolinite

define talc

define tetrahedra

define octahedra

define T-O-T

define T-O

define dioctahedral

define trioctahedral

define interlayer

explain the types of sheet silicate layer arrangements (T-O-T and T-O)

discuss the changes in physical properties based on layer arrangements

discuss the shrink swell ability of expanding clays and why it happens

define pyroxene

d

define amphibole

define pyroxenoid

define enstatite

define ferrosilite

define diopside

define augite

define actinolite

define tremolite

define cummingtonite

define glaucophane

differentiate between orthopyroxene, clinopyroxene, pyroxenoids, and amphiboles in thin section

d

what are the structural differences between pyroxenes, pyroxenoids, and amphiboles

define forsterite

define fayalite

define pryope

d

efine almandine

define kyanite

define sillimanite

define andalusite

define staurolite

explain how we identify different nesosilicates

discuss polymorphism of Kyanite/Sillimanite/Andalusite

how do you identify that a mineral is isotropic like garnet

these are minerals that are the same in all directions. in PPL they appear clear but in PPL they are always black

define beryl

describe why cyclosilicates are typically hexagonal crystal system

define calcite

define aragonite

de

define azurite

de

define malachite

explain differences between calcite and aragonite

discuss compositional similarities between minerals discussed so far in this course

define phosphate minerals

define apatite

define corundum

de

define rutile

define spinel

define brucite

define gibbsite

define bauxite

define geothite

why are hydroxide minerals softer than oxides?

describe where and how must hydroxides form

define/identify halogen

define fluroite

d

define halite

define sylvite

why are halide minerals often water soluble

where do most halide minerals form

define barite

define celestite

define gypsum board

discuss environments where sulfates are likely to form

define galena